What led to the break-up of Pakistan?
Why Pakistan could not survive as a united country? There was a long history of political, economic and cultural causes that eventually developed the demands of provincial autonomy in East Pakistan into a secessionist movement. It might have been saved in March 1971, but the power elites of West Pakistan were not prepared to let the system be transformed into one more acceptable to the East.
Political system in Pakistan broke down in 1971 largely because of the inordinate delay in framing a constitution giving birth to a stable political order, the eclipse of democracy and a deep rooted internal dissension and conflict between East and West Pakistan. The task of constitution-making was hampered due to the divergent perceptions in East and West Pakistan in almost every aspect. While India had agreed on and adopted its constitution by January 26, 1949, it was not until March 7, 1949, that the Pakistan Constituent Assembly drew up what came to be known as the Objectives Resolution and began to concentrate on the task of evolving a constitution. The Constituent Assembly's Basic Principles Committee (BPC) produced its first set of interim proposals in 1950. These were not received with much favor in the eastern wing where the Awami Muslim League (the word Muslim was later dropped) had already been formed as an indigenous political party and a potential rival to the Muslim League. Its leadership was in the hands of Maulana Abdul Hamid Bhashani and Sheikh Mujibur Rehman. The party had drawn up a 42-point manifesto and its foremost demand was complete regional autonomy for East Pakistan "in the spirit of the Lahore resolution," leaving only defense, foreign affairs, currency and coinage with the federal government. The party also called for Bengali to be declared with Urdu as one of the two state languages.
The BPC then produced a second set of proposals which was placed before the Constituent Assembly on December 22, 1952. These provided for parity between the two wings of the country, something that was now strongly resented in West Pakistan which regarded East Pakistan as only one of the five federating units of Pakistan. In the heat of the controversy, the second BPC report virtually fizzled out. It was becoming clear that East Pakistan would be satisfied with nothing short of almost complete autonomy.
In the meantime, General Ayub Khan, who had become the first Pakistani commander-in-chief of the army in 1951 and was to later himself confess to his own political ambitions, teamed up with the Defense Secretary Major General Iskandar Mirza, to consolidate his grip over the levers of power. The civil-military oligarchy at will dismissed and installed governments in the center as well as the provinces, demonstrating an utter contempt for democratic norms. In 1953, Governor General Ghulam Mohammad dismissed Prime Minister Khawaja Nazimuddin using a viceregal prerogative inherited from the days of the British Raj. A year later he also dismantled the Constituent Assembly. His action was, however, condoned by the federal judiciary.
On March 23, 1956, a second Constituent Assembly, with Chaudhry Mohammad Ali (also a former civil servant) as Prime Minister, at last promulgated the first constitution of Pakistan which reflected a consensus. East Pakistan, nevertheless remained alienated from the center because the constitution did not concede to it the expected measure of autonomy.
One can say that it was the agitation for the Bengali language which turned out to be the first schism in the Center-East Pakistan relationship.  The agitation in question was afoot within months of inception of Pakistan and, in fact, immediately after the Quaid-i-Azam had declared in a speech in Dhaka on March 24, 1948, that Urdu and Urdu alone would be the official language of Pakistan: " Let me tell you in the clearest language that there is no truth that your normal life is going to be touched or disturbed so far as your Bengali language is concerned. But let me make it very clear to you that the state language of Pakistan is going to be Urdu and no other language ...... But as I have said, it will come in time. "
A crucial point, however, came four years later, on February 21, 1952, when police opened fire on a demonstration in favor of the Bengali language and three students of Dhaka University were killed. Later a monument called Shaheed Minar was built to commemorate their martyrdom and February 21 was regularly observed as Bengali Language Day in East Pakistan with great fervor. However, little was known in West Pakistan about the episode and the bitterness it had created because the media led the people to believe that after the Quaid-i-Azam's declaration there was no question of East Pakistan not falling in line with West Pakistan in accepting Urdu as the only official language of Pakistan. The people of East Pakistan remained dissatisfied over the language question and after the dominating personality of Mr. Jinnah was removed by his death, discontent became both audible and visible.
Efforts at assimilation were made by developing and encouraging the increased use or at least increased knowledge of Urdu in East Pakistan. In the early days, the provincial government issued an order that in schools where Urdu was the medium of instruction, Bengali must be taught as a compulsory subject and, similarly, where Bengali was the medium of instruction, Urdu must be taught as a compulsory subject. When Molvi Fazlul Haq_XE "Fazlul Haq"_'s party, after defeating the Muslim League took office in 1955, the language order in question was withdrawn. It was a clear indication of the mistrust, as well as strong feeling, which existed with reference to the problem of the national language.
Another crucial point in the history of Center-East Pakistan relationship came in 1954 when the party in power at the Center, the Muslim League was completely routed in the East Pakistan provincial election and the United Front of the opposition parties won more than an overwhelming majority. The United Front fought the election on a 21-point program. The main planks in the manifesto were recognition of Bengali as an official language and complete autonomy for East Bengal in all matters except defense, foreign policy and currency. The manifesto also demanded that the headquarters of the navy be located in East Pakistan and that an armament factory be established in the province. Other demands relating to financial autonomy and East Pakistan's complete freedom from the center with regard to export of jute were bound to create apprehension both among the western elites and business interests.
The election results showed deep revulsions of feeling in the province. The result of this election was that the Muslim League in the East Pakistan Legislative Assembly was swept from power, from office and almost out of sight, for it retained only nine out of 309 seats. In the Constituent Assembly the signals had been read aright and on April 20, 1954, the Muslim League parliamentary party agreed, in terms of a 'Language Formula' that both Urdu and Bengali should be official languages of Pakistan. The language formula was accepted by the assembly on May 7, 1954.
The veteran leader of East Pakistan, Molvi Fazlul Haq, who moved the Pakistan Resolution at the Lahore session of the Muslim League in 1940, became the chief minister and formed the first non-Muslim League government of Pakistan. Within two months he was dismissed being charged with treason and complicity with India and secessionism.  Governor's rule was imposed in the province and Major General Iskandar Mirza was appointed Governor.
The fact of the matter is that the West Pakistan power elite, particularly the army did not trust East Pakistan leaders, even people like Fazlul Haq and Hussain Shaheed Suhrawardy who, inspite of what happened in the preceding years, cooperated with the West Pakistani leaders and the Constituent Assembly and produced the 1956 constitution.Two years later, in October 1958 Ayub Khan abrogated it and imposed martial law, which in retrospect can be seen as a watershed in the history of Pakistan, particularly in the context of the relationship between the two wings of the country.
The great merit of the 1956 constitution was that it represented a consensus between the political leaders of East and West Pakistan. In this East Pakistan surrendered its numerical advantage as a majority province by agreeing to the principle of parity with West Pakistan at the national level. Ayub Khan's martial law upset the entire scheme of things and set the country on a new and uncharted course altogether. It confirmed the worst fears of East Pakistani opinion-makers which they had started entertaining earlier, noticing some straws blowing at the center. Three of the prime ministers hailing from East Pakistan -- Khawaja Nazimuddin, Mohammad Ali (Bogra), and H.S.Suhrawardy -- had either been dismissed or maneuvered out of office by the West Pakistani elite. Ayub Khan's martial law proved to be the proverbial last straw.
The feeling of alienation in East Pakistan continued to aggravate during the Ayub regime. Ayub's election as president in 1965 was considered a hoax. He was elected, inspite of a hostile popular sentiment, under a system of his own making, called Basic Democracy, by an electoral college which could easily be manipulated. Having spent seven years under the yoke of Ayub's military and civil dictatorship, another five-year term for him as president was not seen as a happy prospect. It only added to the feeling of frustration in East Pakistan.
Then came the Indo-Pak war in 1965, another watershed in the history of relationship between East and West Pakistan. Ayub Khan had developed the fatal theory that the defense of East Pakistan lay in the West. During the war which took place on the borders of West Pakistan, East Pakistan was totally cut off. The Pakistanis in that wing of the country were left undefended and completely abandoned to their fate. The theory that the battle of East Pakistan be fought in West Pakistan only added to the feeling of isolation and alienation in East Pakistan.  The 1965 war instead of acting as a great unifying force, as national wars often do, dealt a grievous blow to the incipient process of national integration. The 1965 war thus became the "unfinished agenda" of the 1971 war. Shortly after the 1965 war, signs of political unrest had indeed begun to surface in both wings of the country.