Answer by Balaji Viswanathan:
- Distracted US administration: Nehru timed the aggression within months of JFK taking over. The new administration was still learning the ropes and was too busy focused on the botched "Bay of Pigs" operation in Cuba. When India took the administraton by surprise, all the President could say was a dignified "Oops!"
- Colony or Province? As mentioned bythere was an argument on whether Goa was a province of Portugal or a mere colony. Given that US and Canada were colonies once, they were somewhat sympathetic to India's cause in fighting a colonial power despite Portugal's argument that Goa is a province (who were they kidding?). US didn't want NATO to be seen as siding imperial powers & lose political capital & credibility at a very critical time in Cuba & Vietnam.
- World opinion. Most of the world – from newly liberated colonies in Africa, West Asia, East Asia to USSR & Soviet bloc countries to even China – supported India. NATO's targets are usually isolated countries that no longer have friends (say Milosevic's Serbia or Saddam's Iraq). India had established itself as a leader of the third world and it was politically very expensive to act against India. This was especially important as IndoChina (Vietnam) was starting to boil and any action against India was bound to screw up everything. For most, Goa was too unimportant compared to the action in other places.
- British neutrality. Although Britain was a close friend of Portugal, they also sympathized with the Indian cause and decided to stay neutral. Canada, Australia and other Commonwealth members of NATO were also eager to maintain their relationship with India and were against a NATO action.
- JFK bias. Although the Eisenhower administration (that ruled US until 1960) was more friendly to Portugal, the Kennedy administration that took over in 1961 was more liberal and more sympathetic to India. Nehru timed his takeover of Goa well (waiting for Eisenhower to leave office). It is questionable whether India would have taken over Goa in 1961 if Nixon had won against Kennedy.
Kennedy and Nehru meeting weeks before the Goa liberation
- UN Veto: Portugal and US tried to use the UN for an action. Thanks to USSR Veto, UN Security Council refused to vote against India. This made things even more complicated.
- Personality of Salazar. Salazar (dictator of Portugal) was not a likable figure and as an autocratic dictator he didn't have many friends in the liberal minded members of NATO.
- Weakened administration. Although(US ambassador to the UN) spoke eloquently against India, he had little credibility even in the US. Even his own government did not debrief him regarding the Bay of Pigs crisis and made him appear stupid when talking about the subject in the General Assembly. In short, India's enemies were quite weak at that time and had no political capital to make a significant impact.