(CNN) The attack on a mosque in Egypt that left more than 300 people dead appears to be the deadliest in the history of the Sinai Peninsula.

The triangular mass of land, wedged between the continents of Africa and Asia, is a violent place as ISIS holds onto a foothold in the north of the peninsula and inspires local Islamist extremist groups.

No one has so far claimed responsibility for Friday's mosque attack, but it bears all the hallmarks of ISIS.

Militancy in the Sinai increased dramatically after the overthrow of President Hosni Mubarak in 2011 in the Arab Spring. It was ratcheted up again in 2013 when Mubarak's successor, Mohamed Morsy, was toppled, leaving a security vacuum on the peninsula.

In 2013, Abdel Fattah el-Sisi led a popular coup and launched a major, heavy-handed crackdown on jihadist groups in Sinai and other areas. He resigned from the military and was elected President in 2014 on a platform of security and stability. Egypt outlawed the Muslim Brotherhood, who led the previous government, further fueling resentment.

Read More