The relation between Baekje and Silla became hostile after King Gaeru of Baekje gave refuge to a Sillan treasoner Gilseon in 165, shortly before King Chogo inherited the throne. King Chogo began oppressing Silla in 167 and captured two castles, but the Sillans drove him and his army off.
King Chogo ran another campaign during 188 to 190 against Silla and captured several castles (Castles Mosan, Guyang, Wonsanhyang and Yogeo). He also founded new castles including Castle Jeokhyeon and Sado in captured regions and settled people there in 210.
In 214, he waged war against the Mohe. He led 1000 soldiers to capture Castle Seokmun of Mohe, but the Mohe counter-attacked in the Sulcheon region of Baekje. In July of this year Silla also invaded Baekje and captured Castle Sahyeon.
Baekje (October 18 BCE – August 660 CE) was a kingdom in the southwest of the Korean Peninsula.
King Gaeru is believed to have moved the capital to the Bukhan Mountain Fortress in 132, probably in present-day Gwangju, to the southeast of Seoul.
King Seong, for example, strengthened royal power, but after he was slain in a disastrous campaign against Silla, the nobles took much of that power away from his son.