Boko Haram -- not the Islamic State -- is the world's deadliest terror group .

The Global Terrorism Index says the Nigerian militant group killed 6,644 people in terror attacks during 2014, more than any other terror organization.

There are reports that Boko Haram pledged its allegiance to the Islamic State in March. But allies aside, Boko Haram continued taking credit for its bloody, six-year insurgency in the region in 2015, carrying out mass kidnappings, suicide attacks on mosques and bombings on innocent civilians.

Below is a timeline of the major attacks Boko Haram carried out this year. Click here to learn more about the world's deadliest terror group.