Early career Jacob graduated from the Officers' Training School (OTS) in
Mhow in 1942, and received an emergency commission as a
second lieutenant on 7June. He was initially posted to northern Iraq in anticipation of a possible
German attempt to seize the oil fields of
Kirkuk, and was promoted war-substantive
lieutenant on 7December. In the wake of Japan's defeat, he was assigned to
Sumatra. After World War II, he attended and graduated from artillery schools in England and the United States, specialising in advanced artillery and missiles. As the first commanding officer, he raised
3 Field Regiment on 14 May 1956. On 20 May 1964, he was given command of an artillery brigade, with the acting rank of
brigadier. During the
Indo-Pakistani War of 1965, he commanded an
Infantry Division, which later became the
12th Infantry Division, in the state of
Rajasthan. Jacob was promoted to substantive brigadier on 17January 1966, On 2 October 1967, he was promoted to the acting rank of
major general and was given command of an infantry division, with promotion to the substantive rank on 10 June 1968. On 29 April 1969, he was appointed the chief of staff (COS) of the
Eastern Command, by
General Sam Manekshaw (later
Field Marshal). As the COS, Jacob's immediate superior was
Lieutenant General Jagjit Singh Aurora, the
General officer commanding-in-chief (GOC-in-C) Eastern Command. Jacob was soon tasked with dealing with the mounting
insurgency in Northeast India.
Bangladesh Liberation War signing the
instrument of surrender under the gaze of
J. S. Aurora. Standing immediately behind (L-R)
Nilkanta Krishnan,
Hari Chand Dewan,
Sagat Singh, Jacob (with. Krishnamurthy peeping over his shoulder). Newscaster,
Surajit Sen of
All India Radio, is seen holding a microphone on the right Jacob gained prominence during his stint as the chief of staff of the Eastern Command; the command helped to defeat the
Pakistan Army in
East Pakistan during the 1971
Bangladesh Liberation War. Jacob was awarded a commendation of merit for his role. The action led to over 10million refugees entering India, fuelling tensions between India and Pakistan. By the monsoon season Jacob—as chief of staff—was tasked with drawing the contingency plans in case of a conflict. After consulting with his superior officers, Jacob developed a plan for engaging
Pakistan in a "
war of movement" in the difficult and swampy terrain of East Pakistan. Senior Indian Army officers were reluctant to execute an aggressive invasion for fears of early ceasefire demands by the
United Nations and a looming threat posed by China. Gen. Jacob made Niazi surrender publicly at the
Dhaka racecourse in front of the people of Dhaka, and provided a guard of honour. The war was a significant victory for India, with nearly ninety thousand Pakistani soldiers surrendering to the Indian Army despite only three thousand Indian soldiers in the immediate area of Dhaka. For his role in the war, Jacob was awarded the
Param Vishisht Seva Medal (PVSM) for distinguished service of the most exceptional order. The citation for the PVSM reads as follows:
Later military career On 17 June 1972, Jacob was promoted to the acting rank of
lieutenant general and was appointed as the
General Officer Commanding of
XVI Corps (newly created), with promotion to substantive lieutenant-general on 5 August 1973. His final appointment was as GOC-in-C, Eastern Command, which he held from 1974 until 31 July 1978, when he retired from the Army following 36years of service and having reached the mandatory retirement age. ==Post-retirement life and political career==