who is responsible for Dhaka Fall?

i was sitting with my friend today, and we were having gossip over a cup of tea, in mean time we started talking about Dhaka fall.
   As you all know that Bangladesh was a better half of pakistan, so topic for today is
" Who do you think is responsible for Dhaka fall?"
The options are
1.Pakistan
2. India
3.America
4. or bangladeshi public itself..

comment below to publish your point of view and reasons
and for concerned public please refrain from abuse attacks.... otherwise your comments will not be published... simply