This is a good timeline of relations between Iran and Iraqafter ’79 but it’s only a history in terms of diplomatic relations. The people of the two countries have a long history that predates the modern era. In fact, hundreds of thousands of Iraqi Shi’is are of Iranian ancestry and Baghdad until a couple centuries ago was part of Iran.
The Guardian: 1979 A crucial year in the history of both countries. In February, Ruhollah Khomeini returns to Iran from Paris as leader of the Islamic revolution. In July, Saddam Hussein succeeds the ailing Ahmed Hassan al-Bakr as president of Iraq.
September 1980 Iraqi forces invade Iranian territories, starting a war which lasts for eight years. It is the longest conventional war of the 20th century, leaving more than a million people dead on both sides.
March 1988 Just a few months before the end of the war, Iraq uses chemical weapons against Kurdish rebels in the town of Halabja, just 10 miles from the Iranian border.
1990 After two years of silence, the two countries restore diplomatic relations for the first time since the war. Iran condemns Iraqi invasion of Kuwait, in what is known as the Persian Gulf war, despite newly restored relations.
2000 Improved bilateral relations. Thousands of Iranians pour into Shia holy cities such as Najaf and Karbala.
2002 In a state of the union address, US president George W Bush refers to Iran, Iraq and North Korea as an “axis of evil”, preparing ground for US-led invasion of Iraq in 2003.
2005 Ibrahim al-Jaafari of the pro-Iran Islamic Dawa party leads a transitional government in Iraq after Ahmed Chalabi drops out. In May, Iran’s foreign minister, Kamal Kharazi, goes to Iraq on a ministerial visit. In July al-Jaafari visits Iran and in November President Jalal Talabani becomes the first Iraqi head of state to visit Iran in the history of the Islamic republic.
September 2006 Iraqi Prime Minister Nouri al-Maliki visits Iran for the first time.
March 2008 Mahmoud Ahmadinejad makes an unprecedented visit to Iraq, the first Iranian president to do so in more than three decades.
2009 Tension escalates after Iranian troops briefly cross the border and occupy a disputed oilfield in Iraqi territories.
January 2011 Radical Shia cleric Moqtada al-Sadr, the leader of Iraq’s Sadrist movement, returns to Iraq after three years of living in Iran. Fear grows of Iran’s influence in Iraq.
April 2011 Iraqi forces raid a camp of Iranian dissidents in north-eastern Iraq, killing 34. As part of a crackdown against members of the opposition People’s Mijaheedan of Iran, which helped Saddam during the Iran-Iraq war, the Iraqi government gives an ultimatum to the dissidents to abandon their camp for ever.
July 2011 Iran’s revolutionary guards entered Iraqi territories in the autonomous Kurdistan region, shelling Iraq-based Iranian Kurdish rebels of the Free Life Party of Kurdistan (PJAK). Scores of people on both sides have been killed during the armed conflicts between the two which is still going on.