《元史·本纪·卷二》
太宗四年春，正月初七，太宗由白坡渡过黄河。初九拖雷渡过汉江，派信使来报告，太宗便下诏，命各军前进。三月，太宗命令速不台等包围金朝首都南京。太宗五年春，二月，太宗来到铁列都地方。
戊辰，金西面元帅崔立杀留守完颜奴申、完颜习捏阿不，以南京降。二月，幸铁列都之地。
In the spring of the fourth year of Taizong's reign, on the seventh day of the first lunar month, Taizong crossed the Yellow River at Baipo. On the ninth day, Tolui crossed the Han River, sent a messenger to report it, and Taizong gave an order to the armies to advance. In the third lunar month, Taizong ordered Subedei and others to besiege the Jin Dynasty capital, Nanjing. In the spring of the fifth year of Taizong's reign, in the second lunar month, Taizong reached the Tieletu area.
<s>[INST] Kindly elucidate the central themes in this passage in English: 戊辰，金西面元帅崔立杀留守完颜奴申、完颜习捏阿不，以南京降。二月，幸铁列都之地。 [/INST] In the spring of the fourth year of Taizong's reign, on the seventh day of the first lunar month, Taizong crossed the Yellow River at Baipo. On the ninth day, Tolui crossed the Han River, sent a messenger to report it, and Taizong gave an order to the armies to advance. In the third lunar month, Taizong ordered Subedei and others to besiege the Jin Dynasty capital, Nanjing. In the spring of the fifth year of Taizong's reign, in the second lunar month, Taizong reached the Tieletu area.</s>
Kindly elucidate the central themes in this passage in English: 戊辰，金西面元帅崔立杀留守完颜奴申、完颜习捏阿不，以南京降。二月，幸铁列都之地。
user
In the spring of the fourth year of Taizong's reign, on the seventh day of the first lunar month, Taizong crossed the Yellow River at Baipo. On the ninth day, Tolui crossed the Han River, sent a messenger to report it, and Taizong gave an order to the armies to advance. In the third lunar month, Taizong ordered Subedei and others to besiege the Jin Dynasty capital, Nanjing. In the spring of the fifth year of Taizong's reign, in the second lunar month, Taizong reached the Tieletu area.
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