Silla Seizes the Lower Han River
King Jinheung took the lower Han River that Baekje had just recovered and set up Sinju province, ending the 120-year alliance.

Hoangkid · CC BY-SA 3.0 · Source
Having taken the upper Han from Goguryeo in 551, Silla seized the lower river that Baekje had just recovered in the seventh month of 553. It set up Sinju province there under Kim Mu-ryeok, a prince of the former Geumgwan Gaya royal house.
The Han basin was populous and fertile, and through the port of Danghangseong (Hwaseong) on the west coast it gave Silla direct access to China, which until then it could reach only through Goguryeo or Baekje. It is seen as the step that set the latecomer Silla on the road to unification.
King Seong gave his daughter in marriage to Jinheung that tenth month, but the next year he attacked Gwansan Fortress with Gaya and Wa allies and was killed.