Complex sentence: This war followed the First Indochina War (1946--54) and was fought between North Vietnam--supported by the Soviet Union, China and other communist allies--and the government of South Vietnam--supported by the United States, Philippines and other anti-communist allies.
Split into simpler sentences: This war followed the First Indochina War (1946--54) and was officially fought between North Vietnam and the government of South Vietnam. The North Vietnamese army was supported by the Soviet Union, China and other communist allies and the South Vietnamese army was supported by the United States, Philippines and other anti-communist allies.