Relations between Baekje and the rival kingdom Silla became hostile after Gaeru had given refuge to a Sillan traitor Gilseon in 165, shortly before Chogo inherited the throne.
Chogo ran another campaign (188–190) against Silla, and captured several castles (Castles Mosan, Guyang, Wonsanhyang, and Yogeo). In 204, he destroyed Yocha. He also built new castles, including Castle Jeokhyeon and Sado, in captured territory, and settled people there in 210. The battles occurred around the Sobaek Mountains.
In 214, he waged war against the Mohe. He led 1,000 soldiers to capture Castle Seokmun of Mohe, but the Mohe counter-attacked in the Sulcheon region of Baekje. In July 214 Silla also invaded Baekje, and captured Castle Sahyeon.