Israel says Sinwar and Deif were the masterminds of the Oct. 7 attack in which Hamas-led militants rampaged in southern Israeli communities, killing around 1,200 people and taking some 250 others hostage.

Deif was one of the founders of Hamas’ military wing, the Qassam Brigades, in the 1990s and led the unit for decades. Under his command, it carried out dozens of suicide bombings against Israelis on buses and at cafes and built up a formidable arsenal of rockets that could strike deep into Israel and often did.