Foreign occupation gave the nationalists in the country a common cause to unite.
Step-by-step explanation:
Foreign occupation is a phenomenon that has resulted in many nationalist movements across the world for a long time.
This is because the foreign rule in itself sows the common cause against which the nation can unite itself and then fight back or throw away with diplomacy their own rulers.
This common cause binds the thread of self determination and rule of the nation under one rule is what is requited for nationalism to rise and it happens here rather strongly.
The people of the nation set aside differences against a common enemy of the state.