This was the Soviet invasion and seizure of the Kurile islands group off the north coast of Hokkaido in the Japanese home islands (18 August/1 September 1945).
The operation was undertaken within the context of the 'Manchurian Strategic Offensive Operation' (otherwise 'Avgust Buri'), and was added after the Soviet initial plan to make an amphibious assault on Hokkaido was abandoned for lack of adequate amphibious warfare experience and shipping. The implementation of the 'Kurile Islands Landing Operation' was entrusted to General Leytenant Aleksandr S. Ksenofontov’s LXXXVII Corps of General Leytenant Leonti G. Cheremisov’s 16th Army within General Maksim A. Purkayev’s 2nd Far Eastern Front, and also included elements of General Major Aleksei R. Gnechko’s Kamchatka Defence Area command, ships and transport elements of the Petropavlovsk-Kamchatsky military base, and support by the 128th Airborne Division.
The success of 'Avgust Buri' in Manchukuo and the southern part of Sakhalin island provided the basis for the descent on the Kurile islands group, which was held by Lieutenant General Takashi Tsutsumi’s 91st Division on the northern Shiashkotan, Paramushiro, Shumshu and Onekotan islands, Lieutenant General Torata Sano’s 42nd Division on the north central Shimushir island, the 41st Independent Regiment on the north central Matua island), the 129th Independent Brigade on the south central Urup island, and Lieutenant General Gonnosuke Ogawa’s 89th Division on the southern Iturup and Kunashir islands. under the overall command of Lieutenant General Tsutsumi Fusaki. The Japanese strength in the Kurile islands group was some 51,500 men, while the Soviets deployed only about 15,000 men against them.
The Soviet campaign began with the Battle of Shumshu, which was the invasion of Shumshu as the first stage of the Soviet invasion of this island group. The battle took place between 18 and 23 August, and was the only significant battle of the Soviet campaign in the Kurile islands group and also one of the last battles of World War II. Their success in capturing the island from Japan made it possible for the Soviet forces to take and occupy the rest of the Kurile islands group with any major difficulty.
Despite their recent history of border clashes on the Asian mainland in the late 1930s, the USSR and Japan had maintained a notably scrupulous neutrality after the signature of their neutrality pact on 13 April 1941, although each supported the enemy of the other until the conclusion of the war in 1945. From 1942 to 1945 the USSR steadily rejected requests from the USA for the basing of US warplanes on Soviet territory for operations against Japan and ignored all Allied requests for any form of action which might provoke Japan. However, the Soviet premier, Iosif Stalin, said that the Soviet entry into the war against Japan would not be possible for three months after the defeat of Germany, an assurance he offered to the US ambassador to the USSR, W. Averell Harriman, at a meeting in October 1944, and at the same time demanded major Allied assistance in building up the Soviet forces and the Allied delivery of military supplies in East Asia and the Pacific before the launch of any Soviet campaign against Japan.
The USA quickly began to meet the Soviet requirement over and above its existing Lend-Lease aid, the additional deliveries including the transfer of a dozen types of ships and aircraft across the northern part of the Pacific Ocean from the USA to the Soviet armed forces in Siberia. In 'Hula', during the spring and summer of 1945, the USA transferred 149 ships and less naval craft, mostly escort vessels, landing craft and minesweepers, to the Soviet Navy at Cold Bay in Alaska, but despite this the level of US/Soviet co-operation was very limited and in August 1945 the Soviets still lacked the capability to attempt any major amphibious assault on Japanese territory.
As Stalin had promised, the USSR declared war on Japan on 8 August 1945, exactly three months after Germany’s surrender, and started the huge 'Avgust Buri' strategic offensive against the Japanese forces in north-eastern Asia on the following day. 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.
Another Soviet objective during this period was the occupation of the Kurile islands group which, lying between the southern tip of the Kamchatka peninsula and the north-eastern tip of Hokkaido island, controls access to the Sea of Okhotsk. On 15 August 1945, the commander of Soviet armed forces in the Soviet Far East, Marshal Sovetskogo Soyuza Aleksandr M. Vasilevsky, ordered Purkayev and Admiral Ivan S. Yumashev, commanders of the 2nd Far Eastern Front and Pacific Fleet respectively, to initiate the the conquest of the Kurile islands group by taking Shumshu island and then Paramushiro island at the northern end of this long linear archipelago and just off the southern tip of the Kamchatka peninsula. With these two islands in Soviet hands, the rest of the island chain, which was held only lightly, would fall without undue difficulty.
Purkayev and Yumashev entrusted the undertaking to Gnechko, commander of the Kamchatka Defence Zone, and Captain Dmitri G. Ponomarev, commander of the naval base at Petropavlovsk-Kamchatsky, with Gnechko in overall command. Gnechko and Pomomarev were ordered to assemble an assault force from forces locally available on the Kamchatka peninsula and land on Shumshu within 48 hours.
The Japanese 91st Division garrisoned both Shumshu and nearby Paramushiro, with about 8,500 troops on Shumshu and 15,000 more troops on Paramushiro. The garrisons were able to reinforce one another if necessary, and also possessed 77 tanks. Against this force, Gnechko was able to field two reinforced Soviet infantry divisions and a naval infantry battalion with a combined total of 8,824 officers and men and a naval task force of 64 small vessels to carry them to Shumshu. The Soviets had no tanks and no major warships to commit to the operation, but enjoyed a useful advantage in artillery and mortars.
Gnechko and Ponomarev established the fact that the movement of a force across the 195 miles (315 km) of the world’s foggiest waters from Petropavlovsk-Kamchatsky to Shumshu would take 24 hours, leaving them only 24 hours to assemble and launch 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.
Although Soviet intelligence reports indicated that the Japanese troops on Shumshu were demoralised by Japanese Emperor Hirohito 's announcement on 15 August 1945 that Japan intended to surrender, Gnechko believed that the Japanese advantage in numbers could put the operation in jeopardy. Moreover, the typically difficult weather of the area limited the ability of Soviet aircraft either to undertake preliminary reconnaissance or then to provide support for a landing, but 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 heavy guns: the largest of the vessels, the minesweeper Okhotsk, had only one 130-mm (5.1-in) and two 76.2-mm (3-in) guns. Gnechko also doubted the capability of the Soviet navy to provide enough gunfire support to counter the Japanese coastal artillery, and both he and Ponomarev also believed that the small vessels available would find it very problematical to remain on station and provide effective shore bombardment while under fire from the Japanese coastal batteries and fighting strong currents in the First Kurile Strait.
Gnechko therefore planned to rely on four 130-mm (5.1-in) guns sited on Cape Lopatka, at the southern tip of the Kamchatka peninsula, to provide additional artillery support by firing 13,125 yards (12000 m) across the First Kurile Strait against targets on Shumshu, but appreciated that it was vital for the Soviet landing force quickly to establish a beach-head deep and secure enough to allow Soviet ships to unload artillery and mortars at Shumshu itself: he believed that only then would the Soviet advantage in artillery begin to bear fruit. However, the Soviet ground forces involved possessed little or no experience in amphibious warfare and little time with which to familiarise themselves with Shumshu, and this was another threat the Soviet ability to establish the necessary beach-head. Gnechko hoped that by delivering a tightly concentrated attack on a small area, he would be able to overcome these difficulties and establish a secure beach-head into which the Soviets could swiftly deploy artillery and mortars.
On the other side of the strait, the Japanese 91st Division did not expect a Soviet attack, and also possessed a great familiarity with the terrain as a result of the fact that the Kurile islands group had been a Japanese possession since 1875, and been garrisoned them throughout World War II. Neighbouring Paramushiro had been the major Japanese base in the northern part of the Pacific right through World War II, and Japanese coastal artillery was sited to defend against amphibious assaults on Shumshu. Japanese forces which had fought and were still fighting the Soviets elsewhere in north-eastern Asia had continued to demonstrate an ability to put up a spirited defence so, despite Japan’s announced intention to surrender and the cessation of hostilities with the other Allied powers on 15 August, there was no assurance of Soviet victory.
The Soviet landing force departed Petropavlovsk-Kamchatsky at 05.00 on 17 August and, after a 21-hour passage, reached the First Kurile Strait at 02.00 on 18 August and deployed for the landing on Shumshu. The first wave of about 1,000 naval infantry landed at 04.30 on 18 August. Completely surprised, the Japanese were able to mount only a disorganised defence, but the Soviets were unable to exploit this properly as, inexperienced in amphibious landings, the naval infantry made unco-ordinated advances inland instead of focusing on the primary objective of establishing a secure beach-head of sufficient depth to bring artillery and mortars ashore. By 05.30, after manning their pillboxes and trenches, the Japanese had started to inflict heavy losses on the Soviets with machine gun fire. The Soviets were also slow to begin their attacks on the Japanese coastal artillery positions, which the Japanese defended fiercely. It was only at 06.00 that some first-wave Soviet units finally attempted an attack on the Japanese batteries on Cape Kokutan, but lacked the strength to breach the defences. Even so, the Soviets held off a Japanese infantry counterattack backed by 20 tanks, destroying 15 of the latter, and then charged up the heights toward the artillery sites, but were repulsed near the top.
The Japanese coastal artillery soon found their range against the Soviet naval vessels. 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 0530, led by 16 ex-US Navy large infantry landing craft, the Japanese artillery laid down a heavy fire against it. By the time the Soviet second wave had finished landing at 09.00, Japanese artillery fire had destroyed five of the landing ships. The Soviet second wave landed without artillery and mortars, and with few of its radio sets.
At 09.10, and sorely in need of reinforcements and supplies, the Soviet forces on Shumshu were at last able to establish radio contact with the vessels offshore and with the four guns on Cape Lopatka. The artillery fire from Cape Lopatka was now particularly effective, and the Soviet troops were able to hold out against repeated Japanese counterattacks. By the afternoon, with the weather improving, Soviet warplanes began to attack the naval base on Paramushiro to prevent Japanese reinforcements from reaching Shumshu, and the Soviets had at last established effective communication between the troops ashore, gunfire support ships and warplanes, which combined to inflict heavy casualties on counterattacking Japanese. By the evening of 18 August, therefore, the Soviets had been able to create a beach-head 2.5 miles (4 km) wide and 3.1 to 3.75 miles (5 to 6 km) deep and to bring artillery and mortars ashore.
In a series of attacks during the night of 18/19 August 1945, the Soviets destroyed out most of the Japanese shore batteries' defences, and Gnechko planned 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 91st Division had received orders to end hostilities at 16.00.
The Japanese forces on Shumshu, Paramushiro, and Onekotan signed an unconditional surrender 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 between the Soviets and Japanese in August and September in which Soviet casualties exceeded those of the Japanese. The Soviets suffered 1,567 casualties (516 men killed and 1,051 wounded or missing) and the loss of five landing ships, while Japanese casualties totalled 1,018 (256 men killed and another 762 wounded).
With Shumshu and Paramushiro under Soviet control, the rest of the Kurile islands group, much more lightly held by Japanese forces, fell to Soviet forces without difficulty. The Soviets completed their seizure of the the island group on 5 September.
The initial Soviet reconnaissance of these other islands was undertaken by two mine trawlers carrying a detachment of the 113th Independent Brigade which landed, on 28 August, in Rubetzu Bay on Iturup island. On the same day elements of the LXXXVII Corps landed from torpedo boats, mine trawlers and transports, which had departed Otomari in the captured portion of Sakhalin island, on Kunashir island, Shikotan island and the smaller Sibotzu, Taraku-shima, Uri-shima, Akiuri and Suiseto island groups. The landings on Iturup were continued by the 355th Division, which also landed a detachment on the smaller Urup island.
On 23 August, the 20,000 men of the Japanese garrisons on the invaded islands surrendered as part of the general surrender of Japan, and between 22 August and 1 September the Soviets occupied all of the Kurile islands without further resistance.
The 'Kurile Islands Landing Operation' had cost the Soviets 1,567 men killed or wounded, while the Japanese had lost 1,018 men killed or wounded, and 50,422 men were taken prisoner.