The war began Process_start with isolated clashes Hostile_encounter along the land and maritime boundaries of Vietnam and Kampuchea between 1975 and 1978 , occasionally involving Cause_to_be_included division-sized military formations .

However , the following day the besiegers were assaulted Attack from the back by a Polish division-sized sortie from the Modlin Fortress under Gen. Michał Sokolnicki .