To understand the causes of the 1962 coup, we have to go back a bit further to the past. In 1948, three years after the end of WW2, Burma became independent from the UK. From the onset Burma was to be an unstable nation : in 1947, Aung San, Aung San Suu Kyi’s father and the leader who pushed for independence, was assassinated by a rival politician. The Burmese State had to deal with ethnic conflict, two communist rebellions, and even a Chinese nationalist incursion, with KMT troops occupying parts of the Shan State and trading drugs in the region.
Despite these issues, between 1948 and 1962, Burma was a parliamentary democracy ruled by a civilian government. It had an independent judiciary system, more independent than any government since then. Its constitution was written by 15 Burmese scholars educated in the UK and in theory gave a voice to the minorities living the country. Elections were seen as fair, at least in the regions without any insurgency.
In 1947, U Nu, a devout Buddhist, was elected as the first Prime Minister of Burma. His party, the AFPFL (Anti-Fascist People’s Freedom League) was the largest in the country. It was a large confederation of mostly centre-left parties which adhered in varying degrees to socialism. The party won a large majority of the seats in parliament during the 1947, 1952 and 1956 elections. Inside however the party was quite divided among individual loyalty ties, many individuals in the party had their personal power base, and even their own armed supporters. These tensions led to a split in April 1958, one camp became known as the Clean AFPFL and the other as the Stable AFPFL. They both tried to claim the heritage of the former party.
An election was planned for late 1958. However, as we just saw tensions between the political factions were very high, to the point were civil war was feared, as many politicians were ready to fight to become Prime Minister. At the same time, the communist groups had not been subdued, ethnic rebellions were progressing in the provinces, and Karen rebels even got as far as the outskirts of Rangoon.
Since it joined the allies in later parts of WW2 and participated in the fight for independence , the Burmese military was seen as a honourable institution. A career in the military was considered enviable and higher ups in the military were part of the elite of the country. The military also had experience administrating territories that were under threat from ethnic rebellions or Chinese Nationalists.
Seeing the potential chaos and violence that would result from the 1958 election, Ne Win, the leader of the military, decided to stage a coup. U Nu, who was still Prime Minister at the time decided to legitimise the coup, though it is not clear to what extent he was coerced to do so.
The rule of the caretaker military government was seen as efficient : they reached decisions quickly, were not corrupt, instituted law and order, cleaned the cities and created some successful businesses linked to the military. This period gave great confidence to the military, as they saw themselves as more competent than the civilian government.
However, during this period, there were signs of what was to come : the military imprisoned journalists who criticised its actions, and members of the military took the role of civil servants. While he originally only intended to govern for six months, Ne Win extended his own term twice and stayed 18 months in power, after which the military withdrew and allowed a free election that brought U Nu back into power. Ne Win was also disappointed by the results of this election : he had given his blessing to the candidates of the Stable AFPFL, who lost to U Nu, the leader of the Clean AFPFL.
U Nu, after his re-election in 1960, instead of trying to stabilise the country, decided to make Buddhism the State religion of Burma, which caused a lot of anger and led to the Christian Kachin to take arms against the government. Despite this, U Nu also promised to discuss federalism and minority rights with ethnic leaders.
The military, having tasted power during the caretaker government and finding itself at odds with U Nu’s decisions, decided to stage another coup. Ne Win, the leader of the military, legitimately or not, feared that U Nu’s promises could break up the country. On March 2, 1962, Ne Win launched the coup, during which two people were killed, and took over the government. The official reason was to preserve the unity of the country and avoid chaos.
This time, the military dismantled civilian institutions and arrested anyone who could threaten their rule. Students were massacred for protesting against the new regime. Ne Win created the BSPP (Burmese Socialist Programme Party) and published a manifesto in April 1962. While it adopted some socialist policies, it also rejected Marxism and was infused by nationalism and Buddhism. Ne Win's rule was simply disastrous and turned Burma from the breadbasket of the region to one of the poorest countries in the world.
Unfortunately the reactions of the USA and USSR to this coup are unknown to me (and not mentioned in the sources I used). This new military regime was mostly neutral during the Cold War and was not pro-Soviet or pro-American. It preferred isolationism and was quite xenophobic but had some ties to the nonaligned movement.
Sources :
Burma, What Everyone Needs to Know by David I. Steinberg
Burma, A Nation at the Crossroads by Benedict Rogers
The State in Myanmar by Robert H. Taylor