During the Second World War, it was employed in Home Defence, in Iceland and then in India, where it was temporarily converted back to medium artillery.

However, the decision to transfer the defence of Iceland to the (still neutral) United States had been taken in July 1941, and the AA positions were taken over by US forces later in the year.

[9][20] In December 1941 the regiment sailed (with 165, 201 and 202 Batteries) to India, arriving at Madras in March 1942, 202 Bty moving on to Calcutta shortly afterwards to join 53rd (City of London) HAA Rgt.

At the end of March 1944 the regiment arrived in Galunche, where it came under the AA Brigade of XXXIII Indian Corps.

[9][10][15][21][23][24] In July 1944, by now under 9 AA Bde at Poona, the regiment underwent a major reorganisation, converting back to the medium artillery role.

The reorganised regiment moved to Secunderabad in September, and then to Ranchi in December, where it joined RA Training HQ No 40.

[28] In mid-July 1945, 86 Medium Regiment came under the command of 59th Army Group Royal Artillery, which was training for Operation Zipper, the planned amphibious attack on the coast of enemy-occupied Malaya.

However, when AA Command was disbanded on 10 March 1955, the regiment was placed in suspended animation, completing the process by 1 July.