[9] Recommended by his friend Richard G. Casey, then Governor of Bengal, Cawthorn was sent to Melbourne in 1946 as an Indian representative on the Joint Chiefs of Staff in Australia.

[10] After the Partition of British India, Cawthorn was seconded to the Pakistan Army, where he played a key role in founding the Inter-Services Intelligence (ISI) and served as its first Director General from January to June 1948.

Casey visited Karachi in 1956 and noted that due to Cawthorn's rapport with 'top Pakistanis, we are much better informed than the much larger diplomatic posts.

[14][15] In March 1959, he was appointed High Commissioner of Australia to Canada, and in September 1960, he returned to take the helm of the Australian Secret Intelligence Service (ASIS).

Educated at Melbourne High School, Walter became a schoolteacher alongside his younger sister, Minnie Elizabeth Cawthorn.

Minnie was the third child, followed by sisters Sarah Beryl and Hilda Pauline, brother William, sister Enid Ruth (Cawthorn) Cahill, and brother Colonel Dr. Frank Raymond Cawthorn OBE (1908–1957), a retired officer of the Indian Medical Services who had served in Quetta, World War II, and later as a Quarantine Officer.

[17][18][19][20] Walter married Mary Wyman Varley, a widow and the daughter of Andrew Gillison, on 10 March 1927 at the Marylebone Presbyterian Church in London.

Mary served as an officer in the Women's Auxiliary Corps (India), where she carried out intelligence duties during World War II for four years.

[34] From 1929 to 1930, Cawthorn attended the Staff College, Camberley, after which, on 1 May 1930, he became a company commander in the 4th Battalion, 16th Punjab Regiment, serving on the North-West Frontier.

'[37] By August 1939, Cawthorn was promoted to the local rank of colonel and appointed General Staff Officer Grade 1.

[38][39][40] In this role, he sent Freya Stark on a mission to Imam Yahya's court in Yemen, where she established the Ikhwan al Hurriya (Brotherhood of Freedom), a propaganda network for the British Government which sought to secure Arab support for the Allies.

[42] During the peak of Peter Fleming's career in military deception (1943–1945), Cawthorn, along with Field Marshal Wavell and Louis Mountbatten, was a key supporter.

[43] Promoted to acting Major General from 21 November 1942 to 20 September 1943, Cawthorn also became Deputy Director of Intelligence for the South East Asia Command from October onward.

While his proposal was seen as beneficial for military intelligence, its focus on psychological and political warfare raised concerns, leading Davies to advise against the plan.

Queen Elizabeth II formally presented him with the Companion of the Order of the Bath and the Commander of the British Empire, honors awarded to him years earlier.

Ayub feared that Mirza's presence in Karachi could provoke unrest in the public, so they suggested that he move to Quetta temporarily.

It was this program that drew the attention of an anonymous Australian major general, described as ‘impressive and intelligent’ by Peer de Silva, the CIA Station Chief, during their meeting in mid-1964.

"[54] Cawthorn developed a strong interest in Indonesian affairs and expanded the Jakarta office, making it the largest ASIS station.

"[7] Former Prime Minister Sir Robert Menzies described him to reporters as "undemonstrative" adding, "He was in a sense the quiet man.

"[59] In 1935, Major W. J. Cawthorn of the 4th (Bhopal) 16th Punjab Regiment wrote a pamphlet after visiting Southern Rhodesia to evaluate its suitability for retired British Indian Army officers.

Following a thorough analysis, he concluded: "In my opinion, Southern Rhodesia is a relatively suitable country for permanent settlement by officers of the Indian Army.

If he cannot afford a preliminary visit but believes the conditions would be suitable for him and his wife, I would suggest that he would not be taking an undue risk by coming to this country with the intention of permanent settlement.