Not too difficult, I would think, since to attack Bangladesh Pakistan would need to fight its way clear across India. Which is by itself considerably more militarily powerful than Pakistan.
It was a nasty fight the first time. Myanmar, China, and Pakistan are all buddy-buddy, so perhaps not a cake walk this time either. Consider Spain's role in NATO. Those Russians were going to have to push a long way to get to Spain, but their border wasn't the logical place for the Spanish to start fighting the Russians.