Given the following passage  "In mid-1969, Idris travelled abroad to spend the summer in Turkey and Greece. Gaddafi's Free Officers recognized this as their chance to overthrow the monarchy, initiating "Operation Jerusalem". On 1 September, they occupied airports, police depots, radio stations and government offices in Tripoli and Benghazi. Gaddafi took control of the Berka barracks in Benghazi, while Omar Meheisha occupied Tripoli barracks and Jalloud seized the city's anti-aircraft batteries. Khweldi Hameidi was sent to arrest crown prince Sayyid Hasan ar-Rida al-Mahdi as-Sanussi, and force him to relinquish his claim to the throne. They met no serious resistance, and wielded little violence against the monarchists.",  answer the following question. Note that the answer is present within the text.  Question: When Idris traveled, what happened?
Operation Jerusalem