Question: who led the mongols into russia and conquered kiev
[{'answer': 'Batu Khan', 'provenance': [{'wikipedia_id': '45028', 'title': "Mongol invasion of Kievan Rus'", 'start_paragraph_id': 2, 'start_character': 224, 'end_paragraph_id': 2, 'end_character': 233, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '45028', 'title': "Mongol invasion of Kievan Rus'", 'start_paragraph_id': 13, 'start_character': 0, 'end_paragraph_id': 13, 'end_character': 458, 'bleu_score': 0.9488772845414021, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5106708102084891934}, 'section': 'Section::::Invasion of Batu Khan.\n'}]}]