user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: In which country is the Mekong river located where a military combatant was involved in the Vietnam War? 
Knowledge Triplets: North Vietnam, military.military_combatant.military_conflicts, m.0g5cwl3
North Vietnam, military.military_combatant.military_conflicts, m.04yzp99
North Vietnam, military.military_combatant.military_conflicts, m.062v8cs
m.04z0sqf, military.military_combatant_group.combatants, North Vietnam
m.0chc14c, military.military_combatant_group.combatants, South Vietnam
m.04yvfm8, military.military_combatant_group.combatants, North Vietnam
m.04y_s8z, military.military_combatant_group.combatants, South Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.05cnzgs
South Vietnam, military.military_combatant.military_conflicts, m.09sdkpy
m.03z97td, military.military_combatant_group.combatants, North Vietnam
m.04yw886, military.military_combatant_group.combatants, South Vietnam
m.0478plb, military.military_command.military_combatant, South Vietnam
m.04y_6r1, military.military_combatant_group.combatants, North Vietnam
Vietnam, Cambodia, Laos & the Greater Mekong, book.book.genre, Non-fiction
m.04y__fs, military.military_combatant_group.combatants, South Vietnam
m.04fts61, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04yz302
South Vietnam, military.military_combatant.military_conflicts, m.05nq44r
m.0dls8dn, military.military_combatant_group.combatants, North Vietnam
Mekong Delta, location.location.contains, Hau Giang Province
m.04z2bdv, military.military_combatant_group.combatants, North Vietnam
m.05tfrd3, military.military_combatant_group.combatants, South Vietnam
South Vietnam, military.military_combatant.casualties, m.04kb4kj
Mekong, location.location.partially_containedby, Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.05tbj5p
m.04ywnyf, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04ywny8
m.04z0z3k, military.military_combatant_group.combatants, South Vietnam
m.07slz04, military.military_combatant_group.combatants, North Vietnam
m.04z002c, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04z17nj
South Vietnam, military.military_combatant.military_conflicts, m.04yvh35
Mekong, geography.river.basin_countries, Laos
m.04ywvc3, military.military_combatant_group.combatants, South Vietnam
Mekong, location.location.partially_containedby, China
m.05cl1dh, military.military_combatant_group.combatants, North Vietnam
m.04ywmnk, military.military_combatant_group.combatants, North Vietnam
m.04z0n0q, military.military_combatant_group.combatants, North Vietnam
m.03z97v6, military.force_strength.combatant, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.0dfgcjt
North Vietnam, military.military_combatant.military_conflicts, m.04yx35t
m.04yvh30, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04yvh30
m.04yzp99, military.military_combatant_group.combatants, North Vietnam
Mekong, geography.river.basin_countries, Cambodia
m.0bd31gj, military.military_combatant_group.combatants, North Vietnam
m.04yz_7h, military.military_combatant_group.combatants, North Vietnam
Mekong, book.book_subject.works, Vietnam, Cambodia, Laos & the Greater Mekong
m.05cnn5l, military.military_combatant_group.combatants, South Vietnam
m.04yz37j, military.military_combatant_group.combatants, North Vietnam
m.0b78_7h, military.military_combatant_group.conflict, Joint warfare in South Vietnam, 1963–69
North Vietnam, military.military_combatant.military_conflicts, m.04z35mt
m.04yvf_d, military.military_combatant_group.combatants, South Vietnam
Vietnam War, time.event.locations, Laos
North Vietnam, military.military_combatant.military_conflicts, m.03z97td
South Vietnam, military.military_combatant.military_conflicts, m.04z17np
m.04y_0np, military.military_combatant_group.combatants, South Vietnam
Mekong Delta, location.location.contains, Tien Giang Province
m.04yzp9g, military.military_combatant_group.combatants, South Vietnam
m.0b78mbw, military.military_combatant_group.conflict, Joint warfare in South Vietnam, 1963–69
m.04ywny8, military.military_combatant_group.combatants, North Vietnam
North Vietnamese invasion of Laos, military.military_conflict.combatants, m.0g5cj73
m.04yw_cr, military.military_combatant_group.combatants, North Vietnam
m.0fs6v7n, military.military_combatant_group.combatants, North Vietnam
Laos, location.location.events, Joint warfare in South Vietnam, 1963–69
m.0g5cwl3, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.0bd34v7
m.09j4467, military.military_combatant_group.combatants, North Vietnam
m.0cmxgmm, military.military_combatant_group.conflict, First Indochina War
Laos, book.book_subject.works, Vietnam, Cambodia, Laos & the Greater Mekong
Vietnam, Cambodia, Laos & the Greater Mekong, book.written_work.subjects, Laos
m.04z084z, military.military_combatant_group.combatants, North Vietnam
m.04fvhjs, military.military_combatant_group.combatants, South Vietnam
m.0c1qd3l, military.casualties.combatant, North Vietnam
m.0dlryzb, military.military_combatant_group.conflict, North Vietnamese invasion of Laos
Mekong Delta, location.location.contains, Đồng Tháp Province
m.05t8hr0, military.military_combatant_group.combatants, South Vietnam
m.04yzblp, military.military_combatant_group.combatants, North Vietnam
m.0bd485_, military.military_combatant_group.combatants, North Vietnam
m.04yx35t, military.military_combatant_group.combatants, North Vietnam
m.04yv_4d, military.military_combatant_group.combatants, North Vietnam
m.04y_53f, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04yw881
m.04z1097, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.0g5c27c
m.0ggd4zm, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04z15c1
North Vietnam, military.military_combatant.military_conflicts, m.04ftw8j
Vietnam War, base.culturalevent.event.entity_involved, Thailand
Mekong Delta, location.location.contains, Ca Mau Province
Vietnam, location.location.partially_contains, Mekong
North Vietnam, military.military_combatant.military_conflicts, m.04z002c
m.04yzytw, military.military_combatant_group.combatants, South Vietnam
m.0g5cj73, military.military_combatant_group.conflict, North Vietnamese invasion of Laos
Mekong, location.location.containedby, Asia
m.09sdkpy, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.03z979q
Vietnam, Cambodia, Laos & the Greater Mekong, book.written_work.subjects, Travel
m.0cpk9xf, military.military_combatant_group.combatants, South Vietnam
m.0dfgcjt, military.military_combatant_group.combatants, North Vietnam
m.04y_s8t, military.military_combatant_group.combatants, North Vietnam
m.07llp3_, military.military_combatant_group.combatants, North Vietnam
m.0b798ys, military.military_combatant_group.combatants, North Vietnam
m.04yvqm7, military.military_combatant_group.combatants, South Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04yw886
North Vietnam, military.military_combatant.military_conflicts, m.04yvqm2
Mekong, location.location.partially_containedby, Laos
Mekong Delta, location.location.contains, Kiên Giang Province
m.04y_300, military.military_combatant_group.combatants, South Vietnam
m.0dls8dn, military.military_combatant_group.conflict, North Vietnamese invasion of Laos
North Vietnam, military.military_combatant.military_conflicts, m.04yvfm8
m.04z0g8_, military.military_combatant_group.combatants, North Vietnam
Thailand, location.location.partially_contains, Mekong
m.04yz302, military.military_combatant_group.combatants, South Vietnam
m.0gtztyw, military.military_combatant_group.combatants, North Vietnam
m.02h782s, military.force_strength.combatant, South Vietnam
m.04y_538, military.military_combatant_group.combatants, North Vietnam
m.04yv_4k, military.military_combatant_group.combatants, South Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04z083j
m.04z1mrv, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04fts61
Mekong Delta, location.location.contains, Bến Tre Province
m.07lm3yg, military.military_combatant_group.combatants, North Vietnam
m.04y_df7, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04yvqp7
South Vietnam, military.military_combatant.military_conflicts, m.09j3ckd
m.04z0g94, military.military_combatant_group.combatants, South Vietnam
m.05cnn5f, military.military_combatant_group.combatants, North Vietnam
Mekong Delta, location.location.contains, Tra Vinh Province
m.0czwyb_, military.military_combatant_group.combatants, South Vietnam
m.04yvh35, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04ftr19
m.04kb4l7, military.casualties.combatant, North Vietnam
m.04ywvbz, military.military_combatant_group.combatants, North Vietnam
m.09j3ckd, military.military_combatant_group.combatants, South Vietnam
m.04z15c1, military.military_combatant_group.combatants, North Vietnam
m.05cm_tg, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04z083c
m.05ckv_0, military.military_combatant_group.combatants, South Vietnam
m.04z0z3d, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.0chcw7q
m.04y_qt6, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04z0853
m.04z7_yd, military.military_combatant_group.combatants, North Vietnam
m.02h77fs, military.casualties.combatant, South Vietnam
m.09j4462, military.military_combatant_group.combatants, South Vietnam
m.04yw_cx, military.military_combatant_group.combatants, South Vietnam
Vietnam, Cambodia, Laos & the Greater Mekong, book.book.genre, Travel
m.0chcw7q, military.military_combatant_group.combatants, South Vietnam
m.05cnzgm, military.military_combatant_group.combatants, North Vietnam
Vietnam War, base.culturalevent.event.entity_involved, China
m.04z083c, military.military_combatant_group.combatants, North Vietnam
Joint warfare in South Vietnam, 1963–69, time.event.locations, Laos
South Vietnam, military.military_combatant.casualties, m.02h77gp
m.0bd4cz8, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.09j4462
North Vietnam, military.military_combatant.casualties, m.04kb4l7
m.04fvprj, military.military_combatant_group.combatants, North Vietnam
m.04yvqm2, military.military_combatant_group.combatants, North Vietnam
Vietnam, Cambodia, Laos & the Greater Mekong, book.written_work.subjects, Cambodia
m.0c1qcyn, military.military_command.military_combatant, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.05tfs24
m.0jmy703, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04yvqp2
m.04z083j, military.military_combatant_group.combatants, South Vietnam
m.04z1mrp, military.military_combatant_group.combatants, North Vietnam
m.04y_39h, military.military_combatant_group.combatants, South Vietnam
m.04z0zb9, military.military_combatant_group.combatants, North Vietnam
m.05tbj5v, military.military_combatant_group.combatants, North Vietnam
Mekong, location.location.partially_contains, Cambodia
m.04ml3lw, military.casualties.combatant, North Vietnam
m.04y_64x, military.military_combatant_group.combatants, North Vietnam
m.04ftrvb, military.military_combatant_group.combatants, South Vietnam
m.03z979q, military.military_combatant_group.combatants, North Vietnam
m.04ftx09, military.military_combatant_group.combatants, North Vietnam
Vietnam War, base.culturalevent.event.entity_involved, Thailand
Mekong, travel.travel_destination.tourist_attractions, Adventures by Disney - Cambodia, Vietnam & Laos Vacation
m.03z96cp, military.military_combatant_group.combatants, South Vietnam
m.04kb4kx, military.casualties.combatant, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04ftw4b
m.04y_2_w, military.military_combatant_group.combatants, North Vietnam
Laos, location.location.events, Vietnam War
m.04z002j, military.military_combatant_group.combatants, South Vietnam
Vietnam, location.country.administrative_divisions, Mekong Delta
m.0b79c5w, military.military_combatant_group.combatants, South Vietnam
Mekong Delta, location.location.contains, An Giang Province
m.04y_39b, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04ftrvb
m.062v8cs, military.military_combatant_group.combatants, North Vietnam
Mekong, location.location.partially_containedby, Thailand
m.04ml3l4, military.force_strength.combatant, North Vietnam
m.04z0cm0, military.military_combatant_group.combatants, North Vietnam
m.0c1qd3v, military.casualties.combatant, North Vietnam
Vietnam, Cambodia, Laos & the Greater Mekong, book.written_work.subjects, Mekong
m.04ftr1g, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04z0n0q
South Vietnam, military.military_combatant.military_conflicts, m.04ftw4h
m.04z17nj, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04yzp9g
m.05ckz3p, military.military_combatant_group.combatants, South Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04z0g94
South Vietnam, military.military_combatant.casualties, m.02h77fs
m.04yvf_7, military.military_combatant_group.combatants, North Vietnam
m.04yvsdy, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.06482w8
m.04y_qtc, military.military_combatant_group.combatants, South Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04z18hs
m.04yw881, military.military_combatant_group.combatants, North Vietnam
Vietnam, Cambodia, Laos & the Greater Mekong, common.topic.notable_types, Guidebook
m.04m2vg5, military.military_combatant_group.combatants, South Vietnam
Mekong, location.location.partially_containedby, Myanmar
Mekong, geography.river.basin_countries, Thailand
Vietnam, Cambodia, Laos & the Greater Mekong, book.published_work.published_in_published_as, m.0n5c9r6
m.04z0df9, military.military_combatant_group.combatants, North Vietnam
m.04yv2ck, military.military_combatant_group.combatants, North Vietnam
Mekong, geography.river.basin_countries, China
m.0b797xy, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04yx35z
Mekong, geography.river.basin_countries, Vietnam
m.04yz2_y, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.0dls8dn
m.0n5c9r6, book.contents.work, Vietnam, Cambodia, Laos & the Greater Mekong
m.04z18hs, military.military_combatant_group.combatants, South Vietnam
m.0g5c716, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.03z96cp
m.0cv4v7w, military.military_combatant_group.combatants, North Vietnam
m.04ftw28, military.military_combatant_group.combatants, North Vietnam
m.0b79163, military.military_combatant_group.combatants, North Vietnam
m.0g5c27c, military.military_combatant_group.combatants, South Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04z0z3k
North Vietnam, military.military_combatant.military_conflicts, m.04z1097
North Vietnamese invasion of Laos, military.military_conflict.combatants, m.0dls8dn
South Vietnam, military.military_combatant.military_conflicts, m.04fts66
North Vietnam, military.military_combatant.military_conflicts, m.04ftw28
m.04kb4kj, military.casualties.combatant, South Vietnam
m.05nq44r, military.military_combatant_group.combatants, South Vietnam
m.04z0cd1, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04yz37j
m.04yx8kv, military.military_combatant_group.combatants, North Vietnam
m.04yvqp7, military.military_combatant_group.combatants, South Vietnam
Vietnam War, time.event.locations, Cambodia
Mekong, geography.river.basin_countries, Thailand
m.06wj2w6, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.0chc14c
m.05cldkd, military.military_combatant_group.combatants, North Vietnam
m.05cm_tm, military.military_combatant_group.combatants, South Vietnam
m.04ftybk, military.military_combatant_group.combatants, South Vietnam
m.04z0cm5, military.military_combatant_group.combatants, South Vietnam
m.04z35mt, military.military_combatant_group.combatants, North Vietnam
m.02h783h, military.force_strength.combatant, North Vietnam
m.04z1wmb, military.military_combatant_group.combatants, South Vietnam
m.04z0zbg, military.military_combatant_group.combatants, South Vietnam
m.04yxsw9, military.military_combatant_group.combatants, North Vietnam
m.04fvjr2, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04yxsw9
m.04ftqs2, military.military_combatant_group.combatants, North Vietnam
m.0gb12l8, military.military_combatant_group.combatants, South Vietnam
Mekong Delta, location.administrative_division.country, Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.07lm3yg
m.04y_651, military.military_combatant_group.combatants, South Vietnam
m.04ftyc1, military.military_combatant_group.combatants, South Vietnam
m.05tfs24, military.military_combatant_group.combatants, South Vietnam
m.04fv8nj, military.military_combatant_group.combatants, North Vietnam
m.0g5dgz6, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.0g5c716
North Vietnam, military.military_combatant.military_conflicts, m.07slz04
m.04y_dfd, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.casualties, m.04kb4kx
South Vietnam, military.military_combatant.military_conflicts, m.04yvqm7
m.0cpl3br, military.military_combatant_group.combatants, South Vietnam
m.04fttvx, military.military_combatant_group.combatants, South Vietnam
m.04ftr19, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04ftyc1
m.04yw7ks, military.military_combatant_group.combatants, North Vietnam
m.0b78bs8, military.military_combatant_group.conflict, Joint warfare in South Vietnam, 1963–69
m.04fvk4y, military.military_combatant_group.combatants, North Vietnam
m.04y_br0, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04fv8nj
South Vietnam, military.military_combatant.military_conflicts, m.04m2vg5
m.04ftw4h, military.military_combatant_group.combatants, South Vietnam
m.04y_2zr, military.military_combatant_group.combatants, North Vietnam
Mekong, location.location.partially_contains, China
m.04yw7ky, military.military_combatant_group.combatants, South Vietnam
Mekong Delta, location.location.contains, Soc Trang Province
Vietnam, Cambodia, Laos & the Greater Mekong, common.topic.notable_for, g.1258t0qcw
m.04z0wjv, military.military_combatant_group.combatants, South Vietnam
m.04y_0nj, military.military_combatant_group.combatants, North Vietnam
m.04yvgw7, military.military_combatant_group.conflict, First Indochina War
South Vietnam, military.military_combatant.military_conflicts, m.04ftybk
Mekong, location.location.partially_containedby, Cambodia
m.04ftxwg, military.military_combatant_group.combatants, South Vietnam
m.0bm_4c3, military.military_combatant_group.combatants, South Vietnam
Mekong, geography.river.mouth, South China Sea
m.04yzblv, military.military_combatant_group.combatants, South Vietnam
m.02h77gp, military.casualties.combatant, South Vietnam
m.04z0ccf, military.military_combatant_group.combatants, North Vietnam
m.04fvprp, military.military_combatant_group.combatants, South Vietnam
m.04ftw4b, military.military_combatant_group.combatants, North Vietnam
Mekong, geography.river.cities, Ho Chi Minh City
North Vietnam, military.military_combatant.military_conflicts, m.04ftqs2
m.04yzznh, military.military_combatant_group.combatants, South Vietnam
m.0gx8n8z, military.military_combatant_group.combatants, North Vietnam
m.04yx35z, military.military_combatant_group.combatants, South Vietnam
m.04ftw8j, military.military_combatant_group.combatants, North Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.09j4467
Vietnam, Cambodia, Laos & the Greater Mekong, book.written_work.author, Lonely Planet
m.02h7m00, military.force_strength.combatant, South Vietnam
m.05cnzgs, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04fvprj
m.04y_nm6, military.military_combatant_group.combatants, North Vietnam
m.0bd34v7, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.03z9671
m.04yvqp2, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04z002j
m.04ftw8p, military.military_combatant_group.combatants, South Vietnam
m.09j3ckd, military.military_combatant_group.conflict, War in Vietnam (1954-1959)
m.06482w8, military.military_combatant_group.combatants, North Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04z0zbg
m.02h77tp, military.military_command.military_combatant, South Vietnam
m.05tbj5p, military.military_combatant_group.combatants, South Vietnam
North Vietnam, military.military_combatant.military_conflicts, m.04z084z
South Vietnam, military.military_combatant.military_conflicts, m.04fttvx
South Vietnam, military.military_combatant.military_conflicts, m.05tfrd3
m.04zd3yf, military.military_combatant_group.combatants, North Vietnam
North Vietnamese invasion of Laos, military.military_conflict.combatants, m.0dlryzb
m.03z9671, military.military_combatant_group.combatants, South Vietnam
m.04fts66, military.military_combatant_group.combatants, South Vietnam
South Vietnam, military.military_combatant.military_conflicts, m.04ftw8p
m.05cl1dn, military.military_combatant_group.combatants, South Vietnam
Mekong Delta, travel.travel_destination.tourist_attractions, Adventures by Disney - Cambodia, Vietnam & Laos Vacation
m.04z17np, military.military_combatant_group.combatants, South Vietnam
m.04z2bd_, military.military_combatant_group.combatants, South Vietnam
m.0cpl6jg, military.military_combatant_group.combatants, South Vietnam
Laos, location.location.partially_contains, Mekong
North Vietnam, military.military_combatant.military_conflicts, m.0b79163
m.09vkk7z, military.military_combatant_group.conflict, First Indochina War
Cambodia, book.book_subject.works, Vietnam, Cambodia, Laos & the Greater Mekong
m.0cmxgmm, military.military_combatant_group.combatants, North Vietnam
m.04z0853, military.military_combatant_group.combatants, South Vietnam

Answer: Cambodia
Thailand
China
China