Black Sea . Andreyev oversaw landing and evacuation operations aboard her during the early months of the Axis invasion. From May 1941 until 1943, Andreyev was chief of staff of the Black Sea Fleet. With the
Axis invasion of the Soviet Union in June 1941, he took an active role in developing defensive plans for minelaying, the
Raid on Constanța on 26 June 1941, and the
defence of Odessa. Troops were landed near Grigoryevka and others were evacuated from Odessa on the night of 22 September 1941. During the landing of troops near Grigoryevka, Andreyev was with the headquarters on board the cruiser
Krasny Kavkaz. When the destroyer
Frunze, flagship of the squadron commander
Lev Vladimirsky, was sunk by German aircraft, command temporarily devolved to the landing detachment commander, Captain 1st Rank Sergey Gorshkov. He was promoted to
rear-admiral on 18 April 1943, and to
vice-admiral on 5 November 1944. With the commencement of the
Soviet–Japanese War in 1945, Soviet commanders drew up plans to
capture South Sakhalin. Andreyev and his flotilla was assigned to support the
56th Rifle Corps of the
2nd Far Eastern Front's
16th Army in a complex operation to secure the island. On 8 August the flotilla secretly laid minefields in the
Tatar Strait and
Sakhalin Bay. On 10 August, the flotilla was ordered to land troops in South Sakhalin. The port of
Esutoru was initially selected, but was then deemed too shallow to unload equipment. The port of
Tōro was instead chosen on 14 August, with Andreyev working to land the 365th Marine Battalion, and an accompanying rifle battalion, with support from aviation and naval gunfire. The landings were carried out on the night of 16 August, with the successful capture of the port and surrounding areas, though Andreyev was reprimanded by the front commander for using a rifle battalion without permission and had to return it. Andreyev was next ordered on 15 August to capture the port of
Maoka, beginning the assault on the morning of 20 August with five transports and seventeen ships carrying the 113th Rifle Brigade and a battalion of sailors. Despite resistance, the
Soviet assault on Maoka was a success, and Andreyev flew to Maoka by seaplane to assume command of the operation. From Maoka, Andreyev and the flotilla sailed to
Otomari, arriving on 25 August, when the garrison surrendered. This marked the end of the operation, with South Sakhalin now fully in Soviet hands. From there Andreyev and the flotilla went on to accept the surrender of Japanese troops on the
South Kuril Islands of
Iturup,
Kunashir,
Shikotan, and others. The islands of the
Lesser Kuril Chain were occupied without resistance between 2 and 5 September, and the
Kuril Islands were ultimately all occupied. For his part in this success, Andreyev was awarded the
Order of Ushakov, 1st class. ==Post-war service==