Short Answer 
The timeline begins with Shah Reza Khan’s abdication, leading to his son Mohammed Reza Pahlavi’s takeover. The 1953 CIA-led coup against Prime Minister Mossadegh reinforced the Shah’s reign but sowed the seeds for future dissent, culminating in the 1978 overthrow of the Shah and the establishment of the Islamic Republic of Iran, followed by Iraq’s invasion.
Step 1: The Fall of Shah Reza Khan
The first significant event in this timeline is when Shah Reza Khan stepped down from power. His abdication marked the end of his reign and led to a significant shift in Iran’s political landscape. Following his step down, his son, Mohammed Reza Pahlavi, succeeded him, continuing the monarchical tradition.
Step 2: CIA’s Intervention and the Overthrow of Mossadegh
In 1953, the CIA, along with MI6, played a crucial role in orchestrating the overthrow of Prime Minister Mohammed Mossadegh. The coup was initiated due to fears over Mossadegh’s nationalization of the oil industry, which threatened Western interests. This event solidified the Shah’s power but set the stage for future unrest.
Step 3: Establishment of the Islamic Republic and Iraq’s Invasion
After years of discontent and public protests, the Shah was eventually overthrown in 1978, leading to the establishment of the Islamic Republic of Iran. In the aftermath, Iraq attacked Iran, believing that the country would be vulnerable due to the ongoing revolution. This conflict escalated tensions and marked a significant historical turning point in the region.