| Honorific Prefix: | Lieutenant-General |
| Lionel Protip Sen | |
| Honorific Suffix: | DSO |
| Birth Date: | 1910 10, df=yes |
| Birth Place: | Calcutta, Bengal Presidency, British India (now Kolkata, West Bengal, India) |
| Nickname: | Bogey |
| Allegiance: | (1931-1947)  India (1947-1965) |
| Branch: | |
| Serviceyears: | 1931–1965 |
| Rank: | Lieutenant-General |
| Servicenumber: | AI-77 |
| Unit: | 16/10 Baluch Regiment 8th Gorkha Rifles |
| Commands: | GOC-in-C, Southern Command GOC-in-C, Eastern Command 161st Indian Infantry Brigade |
| Battles: | World War II |
| Awards: | Distinguished Service Order |
| Laterwork: | authored Slender was the Thread |
Lieutenant-General Lionel Protip "Bogey" Sen, DSO (20 October 1910 – 17 September 1981) was a decorated Indian Army general. He served as the Chief of the General Staff during 1959–1961 and commanded the Eastern Command during 1961–1963. He was the general responsible for countering the Chinese invasion of NEFA during the Sino-Indian War of 1962. Sen is also the author of Slender was the Thread, a military history of the Indo-Pakistani War of 1947–1948.
A King's Commissioned Indian Officer (KCIO), Sen attended the Royal Military Academy Sandhurst and was commissioned a second lieutenant in the British Indian Army on 27 August 1931. As was customary, he was attached to a battalion of a regular British Army regiment, the 1st battalion of the Cheshire Regiment, for a period of one year prior to his official appointment to the Indian Army.[1] He was formally appointed to the Indian Army as an officer with the 10th Baluch Regiment on 26 October 1932 (seniority from 29 January 1931). He was promoted lieutenant on 29 April 1933, and to captain on 29 January 1939.
During the Second World War, Sen fought in the Burma Campaign with the 16th Battalion of 10 Baluch. In early 1945, his battalion took a prominent role in the Battle of Hill 170, during which he was awarded the Distinguished Service Order (DSO). The citation recommending Sen for the DSO (which was not published) noted:[2]
...In spite of the greatest difficulties Lt-Col Sen held firmly on to his precarious positions, and the final success of the whole operation was in no small measure due to his dashing assault and tenacious defence. Throughout, he has proved himself a gallant leader of a gallant Battalion and an inspiration to every officer and man under his command.
As the Baluch Regiment, Sen's parent regiment, was among those regiments allotted to Pakistan following Indian independence, Sen transferred to the 8th Gorkha Rifles.
During the Indo-Pakistani War of 1947–1948, he was promoted to acting brigadier and commanded the 161st Indian Infantry Brigade, and ordered to take over the defence of Srinagar and the Kashmir Valley, for which he received a mention in dispatches.[3] [4]
On 23 December 1949, he became Colonel of the 1st Gorkha Rifles (The Malaun Regiment).[5]
On 16 March 1955, Sen was promoted acting major-general and appointed Director of Military Training (DMT). He was appointed Master-General of the Ordnance (MGO) on 8 May 1957,[6] and was further appointed Colonel-Commandant of the Army Physical Training Corps on 26 September.[7]
Sen was promoted to acting lieutenant-general on 1 August 1958, and to the substantive rank on 29 January 1959. On 8 May 1961, he was appointed GOC-in-C, Eastern Command,[8] in which capacity he served during the Sino-Indian War the following year. After the conflict, Sen was appointed GOC-in-C, Southern Command, on 10 May 1963.[9] He retired from this posting on 8 May 1965, after nearly 34 years of service.[10]
In 1939, he married Kalyani Gupta.[11] Their first daughter, Radha, was born in 1941,[12] and Mala in 1947. The marriage ended in divorce in 1953.[13] [14]
Sen died in 1981.[15]
| General Service Medal 1947 | Indian Independence Medal | |||
| Distinguished Service Order | 1939–1945 Star | Burma Star | War Medal 1939–1945 | |
| Insignia | Rank | Component | Date of rank |
|---|---|---|---|
| 27 August 1931 (seniority from 29 January 1931) | |||
| British Indian Army | 29 April 1933 | ||
| British Indian Army | 29 January 1939 | ||
| British Indian Army | 25 August 1940 (acting) 25 November 1940 (temporary) 1 July 1946 (substantive) | ||
| British Indian Army | 22 November 1944 (acting)[16] | ||
| Major | 15 August 1947[17] | ||
| Lieutenant-Colonel | Indian Army | 1947 (temporary) | |
| Indian Army | 1947 (acting) | ||
| Indian Army | 1947 (temporary) 1 January 1950 (substantive, with seniority from 29 January 1949)[18] | ||
| Indian Army | 26 January 1950 (recommissioning and change in insignia)[19] | ||
| Indian Army | 29 January 1952 (substantive) | ||
| Indian Army | 16 March 1955 (acting)[20] 29 January 1956 (substantive)[21] | ||
| Indian Army | 1 August 1958 (acting)[22] 29 January 1959 (substantive)[23] | ||