Question: when did the united kingdom entered world war 2
[{'answer': '1939', 'provenance': [{'wikipedia_id': '20854645', 'title': 'British Empire in World War II', 'start_paragraph_id': 1, 'start_character': 335, 'end_paragraph_id': 1, 'end_character': 339, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '20854645', 'title': 'British Empire in World War II', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 416, 'bleu_score': 0.968982777549629, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17783768144016423031}, 'section': 'Section::::Declaration of war against Germany.\n'}]}, {'provenance': [{'wikipedia_id': '20854645', 'title': 'British Empire in World War II', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ["It also maintained unique political ties to four semi-independent DominionsAustralia, Canada, South Africa, and New Zealandas part of the Commonwealth. In 1939 the British Empire was a global power, with direct or de facto political and economic control of 25% of the world's population, and 30% of its land mass", "When the United Kingdom declared war on Nazi Germany at the outset of World War II it controlled to varying degrees numerous crown colonies, protectorates and the Indian Empire. It also maintained unique political ties to four semi-independent DominionsAustralia, Canada, South Africa, and New Zealandas part of the Commonwealth. In 1939 the British Empire was a global power, with direct or de facto political and economic control of 25% of the world's population, and 30% of its land mass."]}}]}]