The Battle of Mosul was a major battle initiated by Iraq and allied forces to retake the city of Mosul from the Islamic State (IS), which had seized the city years prior in June 2014. It was the largest conventional land battle in the world since the capture of Baghdad in 2003. It was also the world's single largest military operation overall since the 2003 invasion of Iraq and was considered the toughest urban battle since World War II.