In 1980, the Iran-Iraq War began. The longest war of the 20th century. It lasted 8 years.
The reasons are mutual territorial claims, the struggle for oil and leadership in the Islamic world.
The first blow was struck by the Iraqi army under the leadership of Saddam Hussein. He took advantage of the internal political difficulties in Iran. After the overthrow of the Shah, the new government there has not yet had time to get stronger.
Iranian child solider on the front-line of the war
The parties used chemical weapons and even involved children in hostilities. The victims of the war on both sides were 700,000 people killed and about 1500,000 wounded.
In 1988, the fighting stopped, no one won. But Saddam Hussein still dreamed of a small victorious war. And in August 1990, he ordered the invasion of Kuwait.
This was the beginning of the collapse of the dictatorial regime in Iraq.
Image: War on the rocks and Wikipedia