Well here's a story. i watched the interview of Sam Manekshaw. My whole family is his huge fan...
Right before the war, Indira Gandhi called Sam Manekshaw and asked him to led the assault to East Pakistan. Manekshaw said, he can't. On this Indra Gandhi got angry. He then told her, you want to solve the problem of East Pakistan, i will deliver you East Pakistan but you don't interfere in my work same as i will never interfere in yours. He later told that Indra Gandhi when asked him to led the assault, monsoon was almost there and it could change the direction of battle. So he wanted to wait until winter and then led the assault. And look we won a great victory. He said in his interview that he had everything planned. He even said, he wanted US to get involved in that war, so that we could beat US also, but luckily for US that didn't happened.
Indra Gandhi was one of the most powerful leaders we can ever havebut same was Sam Manekshaw. It was believed that Sam Manekshaw had a strong backing from armed forces. If he wanted to act like his conterparts in Pakistan, he could have easily overthrown the Government and ruled but that was never the intention of that great General.
I just wanted to say that Sam Manekshaw didn't needed any kind of backing or approval on the contrary he was so powerful that Indra Gandhi had to support him because of what powerful Generals were doing in Pakistan.