Post-partition, Pakistan confronted obstacles in establishing its army, marked by logistical shortages and strained relations with India. Leadership shifts, from Field Marshal Ayub Khan's modernization efforts to General Yahya Khan's wartime leadership, influenced the army's trajectory. Despite setbacks, the military's resilience set the stage for its significant role in shaping Pakistan's future.

The Teething Problems
Pakistan's independence was a hard-won victory; however, the legacy left by the British created significant tensions between Pakistan and India, culminating in several conflicts since the Partition in 1947. The Kashmir dispute, sparked by the decision of the Hindu Maharaja of Jammu and Kashmir, has been a focal point of these conflicts.
The division of the Indian Army between Pakistan and India commenced shortly before Partition amidst escalating sectarian violence and the Kashmir issue. Despite the planned division, the process was challenging due to the large numbers involved. Out of the 400,000-strong British Indian Army, 260,000 troops were allocated to India and the rest to Pakistan.
Despite efforts towards "Indianization" of the army over the years, a significant number of British officers remained in the Indian Army. Pakistan received a portion of these officers but faced shortages in filling all positions. The shortfall was addressed by retaining some British officers and commissioning others from the ranks or civilian life. Initial cooperation between Pakistani and British officers aimed at establishing a functional army, but later issues arose, particularly regarding promotion criteria.
The division of army units was based on religion, with Pakistan receiving about 30 percent of the soldiers. However, many units were mixed regarding religion, ethnicity, and caste, complicating the process. Disputes over equipment allocation further strained relations, with Pakistan claiming unfair treatment by Lord Mountbatten in ensuring a fair division.
Logistical issues, such as equipment and store shortages, exacerbated the challenges the newly formed armies faced. General Gul Hassan's recollection of receiving obsolete items from India highlights the magnitude of the logistical challenges faced by Pakistan.
Overall, Pakistan's struggle for independence was followed by the arduous task of building a functional army amidst regional tensions and logistical hurdles, reflecting the complexities of the post-Partition era.
The allocation of military equipment and stores to Pakistan was not prioritized by the Indian government or the Governor General, leading to significant obstacles in resolving the issue. Despite discussions in Delhi, it wasn't until October 10, 1947, that a committee was established to address the matter. 
However, Mountbatten concealed the true purpose of this committee from the Supreme Commander, Auchinleck, by misrepresenting its function solely for liaison purposes.
Efforts to negotiate the transfer of stores from India to Pakistan were largely unsuccessful, and Pakistan received only a fraction of what was intended. This shortage of equipment, exacerbated by the diversion of supplies to Sikh irregulars in East Punjab, led to a severe strain on Pakistan's military capabilities.
Auchinleck's protests to New Delhi and appeals to Whitehall went unheard, further exacerbating the tensions. The denial of equipment to Pakistan significantly soured relations between the two countries.
Despite these challenges, Pakistan had the advantage of hosting the Army's Staff College but lacked major defense factories, communication installations, and officer training establishments.
The Disputed Territories
Mountbatten's plan included the establishment of two Boundary Commissions, chaired by Sir Cyril Radcliffe, tasked with delineating the borders of India and Pakistan. Despite Radcliffe's lack of familiarity with the region, his appointment was accepted by both Jinnah and the Congress Party, albeit with reservations from Nehru.
Radcliffe faced a daunting task, arriving in New Delhi on July 8 with only five weeks to demarcate the new national boundaries. Unable to attend all commission meetings simultaneously, he relied on daily reports to inform his decisions, which were deemed final with no possibility of appeal.
Mountbatten, employing charm and persuasion, convinced most princely states to accede to India after Partition, except for Hyderabad, Junagadh, and Kashmir. The latter, with a Muslim ruler but a Hindu-majority population, became a flashpoint of conflict.
By August 1947, the subcontinent was in turmoil. Compounding the situation, the Commander-in-Chief (C-in-C) of the Pakistan Army, General Sir Frank Messervy, was in London, leaving Lieutenant General Sir Douglas Gracey, a British officer, as the acting C-in-C.
The First and Second C-in-Cs of the Pakistan Army 
1. General Sir Frank Walter Messervy, KCCI, KCB, CB, DSO and Bar (August 15 to February 10, 1948).
2. General Sir Douglas David Gracey, KCB, KCIE, CBE, MC and Bar (February 11, 1948 to January 16, 1951). 
Field Marshal Muhammad Ayub Khan (January 17, 1951 to October 27, 1958) 
General Ayub Khan's ascent to the role of C-in-C marked a turning point for the Pakistan Army. While there was speculation about a Pakistani assuming the position after Lieutenant General Gracey, Ayub emerged as a fitting candidate. His tenure, chronicled in his biography, Friends Not Masters, saw significant developments and challenges.
Ayub Khan's biography reflects a tenure characterized by successes and errors, notably highlighted by the war with India in 1965. 
During the 1950s and 1960s, Ayub's leadership significantly influenced the trajectory of the Pakistan Army. This period witnessed military expansion, and notable improvements in training and administration. Apart from navigating involvement in global alliances like SEATO (Southeast Asia Treaty Organization) and CENTO (Central Treaty Organization), Ayub forged strong ties with the U.S., facilitating defense equipment procurement.
Ayub Khan's appointment as C-in-C in 1951 ushered in a new era characterized by comprehensive training programs that modernized and enhanced the effectiveness of the Pakistan Army. His leadership during this pivotal period earned him the title of the "Father of the Pakistan Army."
Ayub recognized the imperative of modernization within the army and swiftly implemented reforms to streamline training and enhance efficiency. Despite challenges in navigating regimental traditions, Ayub prioritized effectiveness over adherence to tradition, successfully enlarging regiments and reorganizing units to bolster capabilities.
Key developments in 1954 reshaped Pakistan's military and foreign policy landscape, including its accession to SEATO and CENTO, which marked significant shifts in the country's stance. The signing of the Mutual Defense Assistance Agreement with the U.S. reflected Pakistan's pursuit of advanced military equipment and asserting foreign policy autonomy.
Ayub's adept navigation of complexities, both militarily and diplomatically, including tensions with India and strategic alliances with the United States, underscored his strategic acumen. While Pakistan sought to leverage these alliances against India, differing expectations ultimately strained relations between Pakistan and the U.S.
Despite challenges, Ayub Khan's tenure left a lasting impact on the Pakistan Army. It set the stage for significant improvements and shaped the country's military and foreign policy trajectories during a critical period of its history.

Early Life
Muhammad Ayub Khan, born on May 14, 1907, hailed from the village of Rehana near Haripur in the Hazara District. He belonged to the Tareen tribe of Pakhtoon ethnicity. The first child of Mir Dad Khan's second wife, Ayub's father, a Risaldar Major in Hodson's Horse, greatly influenced his character and worldview.
Ayub's educational journey began in a school in Sarai Saleh, a few miles from his village, where he commuted on a mule's back. He later moved to a school in Haripur, residing with his grandmother. During his youth, Ayub indulged in sports like kabaddi, gulli danda, marbles, and hockey.
Upon passing his Matriculation Examination in 1922, Ayub enrolled at Aligarh University for four years. However, before completing his B.A. exams, he received an opportunity to attend the Royal Military College at Sandhurst. In 1926, Ayub embarked on a journey to England to pursue military training. Ayub's performance in Sandhurst was exemplary, and he won several scholarships. After successfully training from there, he was inducted as a commissioned officer in 1928 in the British Indian Army. 
Service during WWII
He served the military on various fronts, the Waziristan War (1936-39) and WWII on the Burma front (1944-1945) being two of them. He first served as a Major and then a Colonel. During the communal riots in 1947, he was assigned to assist General Pete Rees in the Punjab Boundary Force. 
Partition and Service with the Pakistan Army
At the time of Independence, Ayub Khan opted to join the Pakistan Army, where, as a Brigadier, he was the senior-most Muslim officer. 
Appointed as C-in-C
In 1951, he became the first native C-in-C of Pakistan, succeeding General Douglas Gracy..
1965 Indo-Pak Skirmishes in the Great Rann of Kutch
Things took an ugly turn in April 1965 due to the souring of relationships caused by skirmishes in the Rann of Kutch, where the Indians attempted to seize Pakistani territory and had to be repelled through swift manoeovres by the Pakistan Army.
1965 Indo-Pak War, September, 1965
The flashpoint of Kashmir brought the two neighbors face to face, providing an opportunity for the armed forces of Pakistan to test their prowess. PAF and Pakistan Navy also came of age during this war, with the PAF claiming air superiority from the third day of the conflict. Simultaneously, the Pakistan Navy launched an attack on the Dwarka base in India, establishing its ascendancy deep into Indian territory.
Fourth C-in-C, General Muhammad Musa Khan, HPk, HJ, HQA, MBE (October 27, 1958 to September 17, 1966). 
General Muhammad Musa Khan Hazara was the fourth C-in-C of the Pakistan Army (1966-1969). He succeeded Field Marshal Ayub Khan, who assumed the Presidency of Pakistan. He was the C-in-C during the crucial Indo-Pakistan War of 1965 and earlier the Rann of Kutch Operations. 
He was the eldest son of Sardar Yazdan Khan and was born on October 20, 1908, in a Muslim Hazara family hailing from Quetta, Pakistan. Khan was from the Sardar family of the Hazara tribe. He was a "Naik" (Non-Commissioned Officer) in the "106^th Hazara Pioneers". Due to his command abilities, he was selected fo commission in the Army and was sent for training at the IMA (Indian Military Academy) at Dehradun in October 1932. He was among the first batch commissioned as a 2^nd Lieutenant (Indian Commissioned Officer) on February 1, 1935. He was first posted to the 6^th Royal Battalion, the 13th Frontier Force Rifles, as a "Platoon Commander". He took part in the Waziristan Operations in 1936-1938. During World War II, He was assigned to the 5^th Infantry Division (India), where he led a Company. He was mentioned in dispatches for 'distinguished services in the Middle East during the period February to July 1941' in the London Gazette on December 30, 1941, as a Lieutenant and acting Major. He was appointed a Member of the Order of the British Empire (Military division) in the London Gazette on April 16, 1942, for 'gallant and distinguished services in the Middle East during the period July to October, 1941'. 
During the partition, he served as a Captain and temporary Major when he opted for the Pakistan Army in 1947. He served with distinction in the Pakistani Army, rose to the rank of General, and was appointed as the C-in-C during President Mohammad Ayub Khan's regime (1958-1969). Becoming C-in-C, he succeeded Field Marshal Ayub Khan.
General Mohammed Musa commanded the Army in the Indo-Pakistani War of 1965 and was responsible for operations throughout the conflict. He was credited for blunting the Indian offensive towards Sialkot during the Battle of Chawinda. He has narrated the events and experiences of the war in his book, My Version. 
Indo-Pak War 1965
General Muhammad Musa is the author of his autobiography Jawan to General, which describes his lifetime experiences from a simple foot-soldier rising to become a general.
After retirement from the Pakistan Army, he served as the fourth Governor of the erstwhile West Pakistan Province (1966 to 1969) and then as the tenth Governor of Balochistan Province (1985 to 1991). He died in office as Governor of Balochistan in 1991.
Fifth C-in-C, General Muhammad Yahya Khan, HPk, HJ, SPk (September 18, 1966 to 20 December 20, 1971)
Born on February 4, 1917, in Chakwal, General Yahya belonged to a Qizilbash family, an ethnic Shi’a Muslim family of Persian descent who could trace their military links to Nadir Shah. He was, however, culturally Pashtun. Nadir Shah was killed in a revolution, and some members of his family escaped from Iran to what later became the Northern Pakistan area. The story is that after the Qizilbash family escaped bare-handed, the family jewels and the small treasure they carried were enough to buy them villages and maintain a royal lifestyle. The Qizilbash family entered the military profession, producing many high-level government officials and generals. 
He attended Punjab University and the IMA, Dehradun, where he finished first in his class. He was commissioned on July 15, 1939, joining the British Army. He was a junior officer in the 4^th Infantry Division (India) during World War II. He served in Iraq, Italy, and North Africa. He saw action in North Africa, where the Axis Forces captured him in June 1942, and interned in a prisoner of war camp in Italy, from where he escaped on the third attempt.
Post-Partition
At the time of the partition of India, in August 1947, he was instrumental in thwarting the efforts of the Indian officers to shift books from the famous library of the British Indian Staff College at Quetta, where Yahya was posted as the only Muslim instructor. He then transferred to Pakistan Army.
Yahya became a Brigadier at the age of 34 and commanded the 106 Infantry Brigade, which was deployed on the ceasefire line in Kashmir (the Line of Control) from 1951 to 1952. 
He was later posted as Deputy Chief of General Staff, where he was tasked with heading the army's planning board by Ayub to modernize the Pakistan Army (1954-57). Yahya also performed the Chief of General Staff duties from 1958 to 1962, from which he commanded the 7 Infantry Division from 1962 to 1965. During the Indo-Pakistani War of 1965, he took over the command of troops and Operations Grand Slam from Major General Akhtar Hussain Malik, and it was there that he was awarded a Hilal-e-Jurat. 
Immediately after the 1965 War, Major General Yahya Khan was promoted to the rank of Lieutenant General and appointed Deputy Army C-in-C and C-in-C designate in March 1966. At every point, as he rose through the ranks, he was the youngest officer to achieve each rank.
He was appointed C-in-C in 1966 and was promoted to the rank of General. In March 1969, Yahya Khan assumed presidential authority, which had been passed on to him by Field Marshall Ayub Khan. 
Sixth C-in-C, Lieutenant General Gul Hassan Khan, SQA, SPk (December 20, 1971 to March 3, 1972)
Lieutenant General Gul Hassan Khan SPk, SQA. Nicknamed George, the 6th and last C-in-C of the Pakistan Army, served from December 20, 1971, until March 3, 1972, the shortest tenure. 
As a young officer, Gul Hassan held the positions of ADC (Aide-de-Camp) to General William Slim and Pakistan’s first Governor General, Muhammad Ali Jinnah. He held coveted appointments as Director of Staff at Pakistan Command and Staff College, Commander of 1 Armoured Division, Chief of the General Staff, Director of Military Operations, and Commander of the 100 Independent Armoured Brigade Group. 
Gul Hassan was known for leading from the front. Notably, he wanted the artillery practice to mimic real war conditions while training army officers. He had a bunker built at the target end of the Muzaffargarh range, which offered some security but wasn't completely safe, as a direct hit could destroy it. Despite the risk, Gul Hassan entered the bunker and instructed the gunners to fire with a narrow margin of error to test their training. He insisted that each artillery regiment take turns firing at the bunker to assess their skills. Colonel E. A. S. Bokhari writes, "Luckily the units fired perfectly, and though General Gul was shaken in the bunker and came out of it with a lot of dust and fear of God in him, but he was quite safe. I have never seen any General Officer do this and ask for fire on a target where he himself was located." 
COAS 
From March 3, 1972, the designation of the C-in-C changed to COAS; their details are as under: