"Marat" took part in the 1937 Coronation Review in Britain. Her participation in the Winter War was minimal as she bombarded Finnish coast defense guns one time at Saarenpää in the Beryozovye Islands with 133 high explosive shells before the Gulf of Finland iced over. In early 1940 her anti-aircraft armament was reinforced. She exchanged her elderly 3-inch "Lender" guns for modern 34-K guns and two twin-gun 76.2 mm 81-K mounts were mounted on her quarter deck. The magazines for these guns were situated in the rearmost casemates on each beam, which lost their 120 mm guns. At some point six automatic 70-K guns were also added. These additions boosted her displacement to at full load. She sailed to Tallinn shortly after the Soviets occupied Estonia, although she returned to Kronstadt on 20 June 1941, two days before the German invasion of Russia began. "Marat" opened fire on troop positions of the German 18th Army from the Leningrad Sea Canal on 8 September. She was lightly damaged by German guns on 16 September.