On 20 July 2015, a suicide bombing in the Turkish-Syrian border town of Suruç perpetrated by an Islamic State of Iraq and the Levant (ISIL) militant led to the deaths of 32 activists from the Socialist Party of the Oppressed (ESP) youth wing. The activists were planning to cross the border to help relief efforts in the Kurdish town of Kobanî, which had been under siege by ISIL militants before being defeated by the Kurdish People's Protection Units (YPG). In retaliation, PKK militants killed two police officers in return for what they saw as collaboration between the Turkish government and ISIL, while ISIL militants directly engaged with Turkish military positions in the border town of Elbeyli, killing one soldier. In retaliation, the government authorised airstrikes against both PKK camps in northern Iraq and ISIL positions in Syria.