The Izz ad-Din al-Qassam Brigades (Arabic: كتائب الشهيد عز الدين القسام‎, lit. 'Battalions of martyr Izz ad-Din al-Qassam'; often shortened to IQB or Al-Qassam Brigades)[12]—also spelt Izzedine or Ezzedeen Al-Qassam Brigades, EQB)[13][14]—named after Izz ad-Din al-Qassam, is the military wing of the Palestinian organization Hamas.[12][15][16] Currently led by Mohammed Deif and its deputy, Marwan Issa, IQB is the largest and best-equipped group operating within Gaza today.[12]

Created in mid-1991,[13] it was at the time concerned with blocking the Oslo Accords negotiations.[17][18] From 1994 to 2000, the Al-Qassam Brigades has claimed responsibility for carrying out a number of attacks against Israelis.[12]

At the beginning of the Second Intifada, the group became a central target of Israel. The group's strength and its ability to carry out complex and lethal attacks surprised many observers. The Al-Qassam Brigades operated several cells in the West Bank, but most of them were destroyed by 2004 following numerous operations of the Israeli Defense Forces (IDF) in the region.[citation needed] In contrast, Hamas retained a forceful presence in the Gaza Strip, generally considered its stronghold. Yahya Sinwar, Hamas political leader in the Gaza Strip since February 2017, is a military leader in the Brigades in Gaza.[19][20]

The Al-Qassam Brigades are explicitly listed as a terrorist organization by the European Union,[21] Australia,[14] New Zealand,[22] Egypt,[23] and the United Kingdom.[24][25] Though not explicitly mentioning IQB, the United States[26][27] and Canada[28] have designated its parent entity, Hamas, as a terrorist organization;[29] Brigade leader Mohammed Deif has also been classified as a Specially Designated Global Terrorist by the US under Executive Order 13224.[30][31] As the Brigades undertake military activity on behalf of Hamas, "organized terrorist activities associated with Hamas can be reliably attributed to the Brigades."