Yiling commands the Yangzi after the gorges, near modern Yichang. In 222 Liu Bei came east to answer Guan Yu’s death. His army camped along the river and faced Wu. Lu Xun refused an early battle, then set the camps on fire. Shu broke, and Liu Bei fell back to Baidi.
The histories use both Yiling and Xiaoting. Xiaoting is the tighter place-name, in modern Xiaoting district. The novel stretches the camps to seven hundred li and has Zhuge Liang foresee the defeat from Chengdu. The fire and the rout are historical. The page on the linked camps separates that exaggeration.
After Yiling, Shu had no realistic way back into Jing province. Wu and Shu made peace again, but the geographic break remained.