Question: who started ww2 and how did it start
[{'answer': 'Nazi Germany', 'provenance': [{'wikipedia_id': '32927', 'title': 'World War II', 'start_paragraph_id': 31, 'start_character': 351, 'end_paragraph_id': 31, 'end_character': 363, 'bleu_score': 1.0, 'section': 'Section::::Pre-war events.:Soviet–Japanese border conflicts.\n'}]}, {'answer': 'on 1 September 1939 with the invasion of Poland by Nazi Germany and subsequent declarations of war on Germany by France and the United Kingdom'}, {'answer': 'with the invasion of Poland by Nazi Germany and subsequent declarations of war on Germany by France and the United Kingdom'}, {'answer': 'begun on 1 September 1939 with the invasion of Poland by Nazi Germany'}, {'provenance': [{'wikipedia_id': '32927', 'title': 'World War II', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 1381, 'bleu_score': 0.674661743928128, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17397224854216059932}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '32927', 'title': 'World War II', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 0, 'bleu_score': 1.0, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17397224854216059932}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '32927', 'title': 'World War II', 'section': 'Section::::Impact.:Casualties and war crimes.\n', 'start_paragraph_id': 136, 'end_paragraph_id': 136, 'meta': {'evidence_span': ['the Baltic states and eastern Poland annexed by the Red Army. The mass-bombing of cities in Europe and Asia has often been called a war crime, although no positive or specific customary international humanitarian law with respect to aerial warfare existed before or during World War\xa0II. The USAAF firebombed a total of 67 Japanese cities, killing 393,000 civilians and destroying 65% of built-up areas. Nazi Germany was responsible for the Holocaust (killing approximately 6 million Jews), as well as for killing 2.7 million ethnic Poles and', 'Nazi Germany']}}]}, {'provenance': [{'wikipedia_id': '32927', 'title': 'World War II', 'section': 'Section::::Pre-war events.:Soviet–Japanese border conflicts.\n', 'start_paragraph_id': 31, 'end_paragraph_id': 31, 'meta': {'evidence_span': ["In the mid-to-late 1930s, Japanese forces in Manchukuo had sporadic border clashes with the Soviet Union and Mongolia. The Japanese doctrine of Hokushin-ron, which emphasised Japan's expansion northward, was favoured by the Imperial Army during this time. With the Japanese defeat at Khalkin Gol in 1939, the ongoing Second Sino-Japanese War and ally Nazi Germany pursuing neutrality with the Soviets, this policy would prove difficult to maintain. Japan and the Soviet Union eventually signed a Neutrality Pact in April 1941, and Japan adopted the doctrine of Nanshin-ron, promoted by the Navy, which took its focus southward, eventually leading to its war with the United States and the Western Allies.", 'Nazi Germany']}}]}]