I am not directly talking about Sundarji here.
The GOI and KGB had plans to "take care of Pakistan" since 1970's.
Indra's plan for a mass invasion was thwarted by the US. Some people suggest that the US had threatened to enter the war.
There's some serious misinterpretation.
It was HENRY KISSKNGER who had suggested that USSR 'd a revisionist and expansionist agenda behind "ostensibly" supporting India to attack West PAKISTAN. But his claim didnot have much proof and nor logic.
On dec 8,1971 CIA reported that India had plans to attack Azad kashmir and attack Pak armour and Air Force.
1) It was NOT a reliable report.It did NOT find many takers in AMERICA itself." NIXON and KISSINGER were virtually alone in US to support this claim" is what Christopher Van Hollen had to say about it.
2) CIA itself had given low priority to this as GEN.Westmoreland and others had argued that INDIA would face logistic obstacles in transferring its military from EAST TO WEST (Indian military was fighting in "East" Pakistan in those days).
2) The fact that Kashmir was a subject of long standing dispute between India and Pakistan and also that "West" Pakistan was not identical to Kashmir. And attack on Kashmir would be thwarted by India and that would not have surprised anyone.
3) INDIA had declared a unilateral ceasefire as soon as it was victorious in East. so this theory gets another thumbs down as it didnot have sufficient proof.
4) AMERICA knew it very well that even IF India had such plans that there would be ample time and clear signals to give a WARNING.
5) USSR was always clear that it's leverage would be to deter Chinese and American interference in East and not at attacking Pakistan.
And it was USSR's support that weakened Pakistan.
And after the success of "East" even USSR had declared ceasefire.
Ergo nowhere did India or USSR show any intention of attacking West Pakistan...that is unless Pak intended to attack Kashmir.
Read- Perceptions and behaviour of Soviet foreign Policy by Richard Herrman.