In May 1919, "Marlborough" conducted tests with new high-explosive 6-inch shells off the Kerch Peninsula, though these proved to be unreliable. During this period, she operated a kite balloon to aid in spotting the fall of shot. Later that month, a shell broke up in the left barrel of "A" turret and caused minor damage. While stationed off the Kerch Peninsula, the ship provided artillery support to White troops, including bombardments of Bolshevik positions in the villages of Koi-Asan and Dal Kamici. By 1920, British attention had turned to the Greco-Turkish War. On 20 June 1920, "Marlborough" arrived in Constantinople, where the Mediterranean Fleet was being concentrated to support the occupation of the city. On 6 July, British forces landed at Gemlik, while "Marlborough" provided artillery support.