In September 1942 Whiteley joined Lieutenant General Dwight D. Eisenhower's Allied Force Headquarters (AFHQ) as the British Deputy Chief of Staff.

After a few months in Germany as Assistant Chief of Staff in the Control Commission, Whiteley was appointed Army Instructor at the Imperial Defence College to initiate the post-war courses under General Sir William Slim as commandant.

He was DCIGS under Slim from 1949 until 1953, when he was promoted to full general, and took up his last appointment, as chairman of the British Joint Services Mission, Washington, D.C., and UK Representative on the NATO Standing Group from 1953 to 1956.

[7] In February 1941, Whiteley conducted a series of meetings with President Franklin D. Roosevelt's emissary to Britain, William J. Donovan, who had been sent to the Middle East on a fact-finding mission.

Whiteley's mission was fairly successful, and resulted in sixteen ships a month for the remainder of the year delivering supplies to the Middle East.

Churchill expressed his displeasure with the progress of the Western Desert campaign,[6] which resulted in Wavell's replacement by General Sir Claude Auchinleck in July 1941.

Amid doubts about Ritchie's suitability for the post, Auchinleck and his new DCGS, Brigadier Eric Dorman-Smith, decided that Whiteley should become Chief of Staff of the Eighth Army.

[12] As such, Whiteley, who was duly promoted to major general in February 1943, was involved in the planning and direction of the Tunisian campaign and the Allied invasion of Sicily (codenamed Operation Husky).

[7] Eisenhower encountered resistance to this from the CIGS, now General Sir Alan Brooke, who agreed to transfer Whiteley and, reluctantly, Gale, but not Strong.

[16] After a few months in Germany as Assistant Chief of Staff in the Control Commission, Whiteley was appointed Army Instructor at the Imperial Defence College to initiate the post-war courses under General Sir William Slim as Commandant.

In 1953 Whiteley was promoted general and took up his last appointment as chairman of the British Joint Services Mission in Washington, D.C., and UK Representative on the NATO Standing Group.

It fell to him as the representative of the British Chiefs of Staff to conduct the discussions on the introduction of tactical atomic weapons and the consequent adjustments to defence plans.