Wikipedia August 25th evokes painful memories in the mind of many Iranians who remember the Anglo-Soviet forces invasion of Iran in this day in 1941 to secure Iranian oil fields and ensure supply lines (Persian Corridor) for the Soviets fighting against Germany on the Eastern Front. The invasion ended on September 17th 1941.
Following Germany's invasion of the USSR in June 1941, the United Kingdom and the Soviet Union became allies. Although a neutral nation, Iran was closer to Germany. This concerned the British who feared that the Abadan Oil Refinery, owned by the Anglo-Iranian Oil Company, might fall into German hands — the refinery produced eight million tons of oil in 1940 and was thus a crucial part of the Allied war effort. For the Soviets, Iran was a country of extreme strategic importance. The German Wehrmacht was steadily advancing through the Soviet Union and there were few ways for the Allies to get desperately needed American Lend-Lease supplies to the Soviets and Trans-Iranian Railway seemed a very attractive route.
The two Allied nations first applied pressure on Iran and the Shah but this led only to increased tensions and pro-German rallies in the capital of Tehran. Reza Shah refused to expel the many German nationals residing in Iran, and denied the use of the railway to the Allies; this, along with the above strategic concerns, prompted Britain and the Soviet Union to launch an invasion of Iran on August 25, 1941.
The invasion was rapid and conducted with ease. Reza Shah appealed to American President Franklin Roosevelt under the Atlantic Charter:
"…on the basis of the declarations which Your Excellency has made several times regarding the necessity of defending principles of international justice and the right of peoples to liberty. I beg Your Excellency to take efficacious and urgent humanitarian steps to put an end to these acts of aggression. This incident brings into war a neutral and pacific country which has had no other care than the safeguarding of tranquillity and the reform of the country." — a letter of August 25.
However, this plea failed to prompt a response from the American President to save the Shah's nation, as Roosevelt's response shows:
"Viewing the question in its entirety involves not only the vital questions to which Your Imperial Majesty refers, but other basic considerations arising from Hitler's ambition of world conquest. It is certain that movements of conquest by Germany will continue and will extend beyond Europe to Asia, Africa, and even to the Americas, unless they are stopped by military force. It is equally certain that those countries which desire to maintain their independence must engage in a great common effort if they are not to be engulfed one by one as has already happened to a large number of countries in Europe. In recognition of these truths, the Government and people of the United States of America, as is well known, are not only building up the defenses of this country with all possible speed, but they have also entered upon a very extensive program of material assistance to those countries which are actively engaged in resisting German ambition for world domination."
Roosevelt also reassured the Shah by noting "the statements to the Iranian Government by the British and Soviet Governments that they have no designs on the independence or territorial integrity of Iran". However, the Soviets would later back separatist states in the north, while the U.S. and UK would later support the overthrow of the popular and democratically elected Iranian Prime Minister Mohammed Mossadegh during the Abadan Crisis in 1953.
The campaign began on August 25 with a dawn attack by the British sloop HMS Shoreham on the harbour at Abadan. The Iranian sloop Palang was quickly sunk, and remaining ships were destroyed or captured. Resistance had not had time to prepare and the oil installations at Abadan were captured by two battalions from 8th Indian Division's 24th Indian Brigade making an amphibious crossing of the Shatt al-Arab from Basra. A small force was also landed at Bandar-e-Shahpur from the armed merchant cruiser HMAS Kanimbla to secure the port and oil terminal there. The Royal Air Force attacked airbases and communications. 8th Indian Division (18th Brigade plus 25th Brigade under command from 10th Indian Division) advanced from Basra towards Qasr Shiekh (which was taken on August 25) and by August 28 had reached Ahwaz when the Shah ordered hostilities to cease. Further north, 8 battalions of British and Indian troops under Major-General William Slim advanced from Khanaqin (100 miles north east of Baghdad and 300 miles from Basra) into the Naft-i-Shah oilfield and on towards the Pai Tak Pass, leading towards Kermanshah and Hamadan. The Pai Tak position was taken on August 27 after the defenders had withdrawn in the night and the planned assault on Kermanshah on August 29 was aborted when the defenders called a truce to negotiate surrender terms.
The Soviets invaded from the north and advanced toward Maku, which had been softened up by bombing raids. There were also Soviet landings at Bandar-e Pahlavi, on the Caspian coast. In one incident, Soviet ships suffered from "friendly fire".
In naval actions, 2 Iranian warships were sunk and 4 crippled by the Royal Navy. Six Persian fighters were shot down. Approximately 800 Iranian soldiers, sailors, airmen were killed, including Admiral Bayandor. Approximately 200 civilians died in Russian bombing raids in Gilan. British and Indian casualties were 22 killed and 42 wounded.
Without anyone to step in and save Iran, Iranian resistance had been rapidly overwhelmed and neutralised by Soviet and British tanks and infantry. The British and Soviet forces met at Senna (100 miles west of Hamadan) and Kazvin (100 miles west of Tehran and 200 miles north east of Hamadan) on August 30 and 31 respectively. Iran was defeated, the oilfields safeguarded and the valuable Trans-Iranian Railway was in Allied hands. Because of lack of transport the British decided not to establish any forces beyond Hamadan and Ahwaz. In the meantime, the new Persian Prime Minister, Fourughi, agreed that the German Minister and his staff should leave Tehran, the German, Italian, Hungarian and Romanian legations be closed and all remaining German nationals be handed over to the British and Soviet authorities.
The failure to meet the last of these conditions led to British and Soviet troops entering Tehran on September 17, the day after Reza Shah had been arrested and sent into exile in South Africa, leaving his son Mohammad Reza Shah Pahlavi to replace him on the throne. The Soviet and British forces withdrew from Tehran on October 17, after the German agents had been dealt with although Iran was effectively divided between Britain and the Soviet Union for the duration of the war.
Picture from Tehran Conference, Nov. 28–Dec. 1, 1943, meeting of President Franklin Delano Roosevelt, Prime Minister Winston Churchill, and Premier Joseph Stalin at Tehran, Iran. The conference was held to strengthen the cooperation of the United States, Great Britain, and the USSR in World War II.
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Iran's failure to hand over Germans to the British and Soviet authorities led to British and Soviet troops entering Tehran on September 17. "
The two Allied nations first applied pressure on Iran and the Shah but this led only to increased tensions and pro-German rallies in the capital of Tehran. Reza Shah refused to expel the many German nationals residing in Iran, and denied the use of the railway to the Allies; this, along with the above strategic concerns, prompted Britain and the Soviet Union to launch an invasion of Iran on August 25, 1941. 
The Soviets invaded from the north and advanced toward Maku, which had been softened up by bombing raids. There were also Soviet landings at Bandar-e Pahlavi, on the Caspian coast. In one incident, Soviet ships suffered from "friendly fire".
