The 'Battle of Shumshu' was fought between Soviet and Japanese forces for Shumshu, the most northerly of the Kurile islands group between Kamchatka and Hokkaido (18/23 August 1945).

The battle was the first stage of the Soviet 'Kurile Islands Offensive Operation' to seize the Kurile islands group, which separates the Sea of Okhotsk to its west and the Pacific Ocean to its east, and was the only significant battle of the Soviet campaign in the island group and one of the last battles of World War II.

The USSR and Japan maintained an armed neutrality, which was sometimes fraught, between each other after the signing of the Soviet-Japanese Neutrality Pact on 13 April 1941, although the two countries were allied with each other′s World War II enemies from 1941 until the conclusion of the war in 1945. The USSR refused Allied requests for any actions which might provoke Japan, but discussed plans to base US aircraft on Soviet territory for operations against Japan after the Soviet declaration of war on Japan.

Iosif Stalin had earlier informed the USA and UK that the Soviet entry into the war against Japan would not be possible until after a three-month period following Germany’s defeat: this was an assurance he had offered to the US ambassador to the USSR, W. Averell Harriman, at a meeting in October 1944. Stalin further stipulated as part of the agreement that it would need an Allies provision of substantial assistance to the USSR in building its armed forces, and also military supplies in East Asia and the Pacific, in advance of any Soviet operations against Japan. The USA soon began to meet the Soviet requirements both within and without its annual Lend-Lease allotments of aid to the Soviets, including the transfer of a dozen types of ships and aircraft from the USA to the Soviet armed forces. In the spring and summer of 1945, in 'Hula', the USA secretly transferred 149 ships and craft, most of them escort vessels, landing craft and minesweepers, to the Soviet navy at Cold Bay in Alaska. Even so, co-operation between the Soviets and Americans was minimal and in August 1945 the Soviets still lacked the capability to make a major seaborne invasion of Japanese-held territory.

As Stalin had promised, the USSR declared war against Japan on 8 August, exactly three months after Germany’s capitulation, and on the following day began their 'Manchurian Strategic Offensive Operation' against Japanese forces in north-eastern Asia. During August, Soviet forces attacked Japanese forces in the puppet state of Manchukuo in Manchuria, in the Japanese province of Karafuto on the southern half of Sakhalin island, and the northern half of Korea, at that time a Japanese possession. Another Soviet goal during the offensive was the occupation of the Kurile islands group.

On 15 August, the commander-in-chief of Soviet armed forces in the Soviet Far East, Marshal Sovetskogo Soyuza Aleksandr M. Vasilevsky, ordered the commander of the Soviet army’s 2^nd Far Eastern Front, General Leytenant Maksim A. Purkayev, and the commander of the Soviet navy’s Pacific Fleet, Admiral Ivan S. Yumashev, to take the first step in the conquest of the Kurile islands group by occupying Shumshu, an island 150 sq miles (388 km²) in area, and Paramushiro, an island 793 sq miles (2053 km²) in area, at the northern end of the archipelago, just off the southern tip of the USSR’s Kamchatka peninsula. The Soviet forces were first to take Shumshu and then Paramushiro, and with these two islands under Soviet control, then to seize the rest of the island chain, which was believed to be held only lightly and would therefore be likely to fall easily.

Purkayev and Yumashev placed the commander of the Soviet Kamchatka Defence Zone, General Aleksei R. Gnechko, and the commander of the naval base at Petropavlovsk-Kamchatsky, Kapitan 1-go ránga Dmitri G. Ponomarev, in charge of the Shumshu operation, with Gnechko in overall command. Gnechko and Pomomarev had orders to assemble an assault force from the army formations and units locally available on the Kamchatka peninsula and to make a landing on Shumshu island within 48 hours.

The Imperial Japanese army’s 91^st Division, under the command of Lieutenant General Tsutsumi Fusaki, garrisoned both Shumshu and nearby Paramushiro with about 8,500 men on Shumshu and 15,000 men on Paramushiro. The garrisons were able to reinforce each other if necessary. The Japanese strength also included 77 tanks. Against this force, Gnechko was able to field two reinforced army infantry divisions and one naval infantry battalion with a combined total of 8,824 officers and men and a naval task force of 64 small ships and craft to carry them to Shumshu. The Soviets had no tanks and no major warships with which to support the operation, but enjoyed a significant superiority in artillery and mortars.

Gnechko and Ponomarev assessed the daunting schedule laid on them, concluding that the movement of a force over the 195 miles (315 km) from Petropavlovsk-Kamchatsky to Shumshu, across the world’s foggiest waters, would itself take 24 hours, leaving the Soviets only 24 hours to assemble an assault force if they were to meet the requirement to land on Shumshu by the evening of 17 August. Gnechko requested and received a 24-hour postponement, which moved the landing requirement to no later than the evening of 18 August.

Although Soviet intelligence reports indicated that the Japanese troops on Shumshu were demoralised by Emperor Hirohito’s announcement of 15 August that Japan intended to surrender, Gnechko believed that the Japanese advantage in numbers could put the Soviet operation in jeopardy. Chronically poor weather in the area limited the ability of Soviet aircraft to conduct reconnaissance or provide support to a landing, but warplanes were tasked to attack Paramushiro’s naval base to interdict Japanese reinforcements attempting to reach Shumshu.

Gnechko also feared that his force lacked sufficient artillery and naval gunfire support for its initial landing. The ships of the landing force had few large guns, for the largest of the Soviet vessels, the minesweeper Okhotsk, had only one 130-mm (5.12-in) and two 76.2-mm (3-in) guns, and he doubted the Soviet navy’s ability to provide sufficient gunfire support to counter the Japanese coastal artillery. Moreover he and Ponomarev doubted the ability of the small ships available to remain on station and provide effective shore bombardment while both under fire from Japanese coastal batteries and fighting strong currents in the First Kurile Strait.

Gnechko planned to rely on four 130-mm (5.12-in) guns on Cape Lopatka on the southern tip of the Kamchatka peninsula to provide additional artillery support by firing 7.5 miles (12 km) across the First Kurile Strait against targets on Shumshu, but saw it as critical that Soviet infantry quickly establish a beach-head which was deep and secure enough to allow Soviet ships to unload artillery and mortars at Shumshu itself. Gnechko believed that only then would the Soviet advantage in artillery begin to express itself. However, the Soviet ground forces to be committed had little or no experience in amphibious warfare and little time for familiarisation with Shumshu itself, and this too threatened the Soviet ability to establish the beach-head which was required. Gnechko hoped that by focusing the landing force in a concentrated attack on a small area, he could overcome these difficulties and establish a secure beach-head on which artillery and mortars could quickly be sited.

On the Japanese side, the 91^st Division did not expect a Soviet attack. However, the Kurile islands group had been a Japanese possession since 1875, and Japanese forces had garrisoned them throughout World War II, giving them a useful tactical familiarity with the terrain. Nearby Paramushiro island had been the major Japanese base in the North Pacific during the war, and Japanese coastal artillery was sited to defend against amphibious assaults on Shumshu. The Japanese forces fighting the Soviets elsewhere in north-eastern Asia had demonstrated an ability to put up a spirited if futile defence, despite Japan’s announced intention to surrender and the cessation of hostilities with the other Allies as of 15 August 1945.

The Soviet landing force departed Petropavlovsk-Kamchatsky at 05.00 on 17 August and, after a 21-hour passage, reached the 1^st Kurile Strait at 02.00 on 18 August and then took up positions for the landings on Shumshu. The first wave of about 1,000 naval infantrymen went ashore at 04.30 on 18 August and, completely surprised, the Japanese were able to respond with only a disorganised defence. The Soviets were unable to exploit this advantage properly, however, as the naval infantrymen were inexperienced in amphibious landings and made unco-ordinated advances inland instead of focusing on the primary objective of establishing a secure beach-head of sufficient depth to allow artillery and mortars to be brought ashore. By 05.30, the Japanese had manned machine guns in pillboxes and foxholes, and begun to inflict heavy casualties on the Soviets. The Soviets also took too long to begin their assaults against the Japanese coastal artillery positions, which the Japanese defended fiercely. At 06.00, some first-wave Soviet units belatedly attempted an attack on the Japanese batteries on Cape Kokutan, but were outnumbered sand failed to breach the defences. The Soviets held off a Japanese infantry counterattack supported by 20 tanks, destroying 15 of the latter, and then charged up the heights toward the artillery sites only to e driven back near the top.

The Japanese coastal artillery soon found the range of the Soviet ships. Almost completely lacking radio communication with the troops ashore, the Soviet ships' attempts at naval gunfire support were ineffective. When the Soviet second wave headed for shore at 05.30, led by 16 ex-US Navy large infantry landing craft, the Japanese artillery engaged it with heavy fire. By the time the Soviets had finished unloading the second wave at 09.00, Japanese artillery fire had destroyed the landing ships DS-1 (ex-LCI(L)-672), DS-5 (ex-LCI(L)-525), DS-9 (ex-LCI(L)-554), DS-43 (ex-LCI(L)-943) and DS-47 (ex-LCI(L)-671). The Soviet second wave landed without its artillery and mortars and with few of its radios.

At 09.10, Soviet forces on Shumshu were in sore need of reinforcements and supplies, but finally established radio contact with the ships offshore and with the four guns on Cape Lopatka. The fire from this latter was particularly effective, and the Soviet troops held out against repeated Japanese counterattacks. By the afternoon, and with the weather improving, Soviet aircraft began to attack the naval base on Paramushiro to prevent Japanese reinforcements from being despatched to Shumshu, and the Soviets had established good communications between their troops ashore, gunfire support ships, and aircraft, which combined to inflict heavy casualties on counterattacking Japanese. By the evening of 18 August, the Soviets had established a beach-head 2.5 miles (4 km) wide and 3.1 to 3.75 miles (5 to 6 km) deep, and had managed to bring ashore both artillery and mortars.

In a series of attacks during the night of 18/19 August, the Soviets wiped out most of the defences of the Japanese shore batteries, and Gnechko made plans to bring all Japanese resistance on Shumshu to an end on 19 August. Soviet heavy artillery came ashore on the morning of 19 August, and small groups of Japanese began to surrender. At 09.00, a Japanese envoy informed the Soviets that the 91^st Division had received orders from higher command to cease hostilities at 16.00.

The Japanese forces holding Shumshu, Paramushiro and Onekotan islands signed an unconditional surrender agreement at 18.00 on 19 August, but fighting on Shumshu continued to flare up until 23 August, when the last Japanese on the island finally surrendered.

The 'Battle of Shumshu' was the only battle of August and September 1945 between the Soviets and the Japanese in which Soviet casualties exceeded those of the Japanese: the Soviets suffered 1,567 casualties (516 killed or missing and 1,051 wounded) and the loss of five landing ships, while the Japanese losses totaled 1,018 men (256 killed and 762 wounded). Soviet officers later said that the operation demonstrated the difficulty of amphibious operations on a defended coast, and also the Soviet shortfalls and inexperience in amphibious warfare. These factors, they claimed, were the reasons for their cancellation of the planned 'Hokkaido Offensive Operation''.

With Shumshu and Paramushiro under Soviet control, the rest of the Kurile islands chain, much more lightly held by Japanese forces, fell to Soviet forces easily. The Soviets completed their occupation of the Kurile islands group on 5 September.