What Chocolate and ghr2 said.
I could elaborate on this but let’s just give the example of one of the games I played:
UK marched towards India with around 60 units@120 combat factors. Not 100% sure about the number of units but the combat factors I remember… The UK pulled out before Japan could attack India (round 6) and merged that army with the incoming troops from the Middle East. Then liberated Calcutta round 9.
Chasing the retreating troops can be difficult if the RAF is in Range of west-India…