Complex sentence: During invasions of Esen Tayisi from 1446--48, most of them fled, however, Fuyu Guard of the Three Guards remained along the Nen River and Onon River.
Split into simpler sentences: During invasions of Esen Tayisi in 1446--48, most of the guards fled. However, the Fuyu Guard, another of the Three Guards, remained along the Nen River and Onon River.