Complex sentence: Other than expanding, Guo Jia's other purpose in Xuzhou was to gather food supply for future campaigns but were unexpectedly defeated by the teaming up of Zhuge Liang and Sima Yi; the two met on their way to Xuzhou and decided worked together to defend Xuzhou.
Split into simpler sentences: Other than expanding, Guo Jia's other purpose in Xuzhou was to gather food supply for future campaigns but were unexpectedly defeated by the teaming up of Zhuge Liang and Sima Yi. The two met on their way to Xuzhou and decided worked together to defend Xuzhou.