最终，要塞被入侵的军队攻陷了。

Eventually, the fortress ___fell to the invading army.

经过漫长的内战，旧政权垮台，新政府得以建立。

After a prolonged civil war, the old regime ___fell and a new government was established.

在被完全切断补给后，这座被围困的首都沦陷了。

The besieged capital ___fell after its supplies were completely cut off.