Occupation of Iran in World War 2

The allied forces , Britain , Russia specially and France had always a bad record in Iran and that has nothing to do with GERMANY. Iran had always good relations with Germany much before Hitler, Check for Wassmus of Persian in google. Iran did not have any sympathy for Nazi racism. They cared about protecting their jews which was the largest in Middle East then. Iran told Hitler that Iranian jews were assimilated Iranian of Aryan descendents and that he can't touch them. Iran gained a special status for it jewish population. Meanwhile Reza shah after cyrus the great is very popular among jews, because jewish organisations and rights improved under him and his son. His secular policy intended to include and unify all Iranians of any tribe or religion or ethnicity together. Reza Shah benefited from German engineers who unlike Brits were not involved in looting Iran and its resources. German engineers did a good assistance. Brits and Russians did not respect Iran's neutrality just because Brits wanted to secure Abad oil field through BP, then called Anglo Iranian company. Reza shah did not like Brits dirty politics of dividing Iran and its Darcy oil contract under Qajar. Russia was always wishing to occupy and separate lands from Iran. It was peter great wish to put his boots in warm waters (Persian Gulf).

The Invasion of Iran was carried out by British and Commonwealth forces in the south, and Soviet forces in the north. The Shah of Iran was forced to abdicate, and the new Iranian government under his son was obliged to adopt a pro-Allied stance. For the remainder of the war, Iran was occupied by Soviets in the north and British forces in the south. The occupation continued until 1946.

Why Was Iran Occupied?

It is naive to claim that Iran had nothing to do with "their war". Iran was of great strategic importance to the Allied war effort; the Allies would not tolerate a pro-German Iran.

Iran however, have a history of business with Germany, and when WW2 began, the Iranian government sought to pursue a policy of neutrality. Unfortunately, that failed to reassure the Allies. Therefore between July and August 1941, Britain issued two ultimatums demanding Germans be expelled from Iran. The Iranians refused, and the Allied invasion began on 25 August.

The main motivations of the Allies were:

• Securing a vital supply route into Russia: the Persian Corridor enabled massive movements of supplies through to both the Soviet Union as well as Middle Eastern British forces. Some 30% of Lend-Lease shipments to the Soviets were made through this route.
• Safeguarding Iranian oil supplies: the British Anglo-Iranian Oil Company refinery in Iran was a significant part of the Allied war effort; conversely, it was crucial to deny oil to the German army.

Why Didn't Hitler Try to Stop it?

I'm not really sure what you expect Hitler to do. Axis forces were separated from Iran by Turkey, the Soviet Union, and British controlled Iraq. In contrast, the Allies had sizeable forces already deployed around Iran. Unfortunately, Nazi Germany had no success in developing a mass teleportation device.

Even if Hitler tried to do anything, there is nothing he could do to materially change the military situation on the ground. So no, it would not have given him "a good chance of winning the war". Even if Iran threw itself behind Nazi Germany, the military balance of power in the region was so tilted against them that it would have been little more than a rerun of what had only just happened to Iraq.

Why Weren't the Allies Questioned in Court?

I'm not sure how you imagined that could possibly happen. Or in what court that could possibly happen.

No court had jurisdiction over the Allies. None of the Allies would have agreed with your claim that it is a "crime", much less allowed Iran to take them to any court over it. And most importantly, as victors of the bloodiest war in human history, the Allies of 1945 could hardly be compelled otherwise. Even the International Court of Justice would have required their consent to have jurisdiction.

In any case, the international law prescript against the use of force in international conflicts was a development since 1945. And even now great powers still discard them at will, as evidenced by recent news. It isn't as though there actually is an international police who would come around and take you to trial.