On Sept. 8, the US State Department unexpectedly added three Hamas leaders to its blacklist of Specially Designated Global Terrorists, freezing their US assets and prohibiting its citizens from doing business with them. The move against Mohammed al-Deif, Yahya Sinwar and Rawhi Mushtaha is prompting speculation on what might have motivated the United States to act now.

According to the State Department's website, the three Hamas leaders are known for their roles in founding Hamas’ military wing, Izz ad-Din al-Qassam Brigades, in 1991, and for planning armed attacks against Israel.

This is probably the first time Washington has described Hamas leaders as terrorists, although it classified Hamas itself as a terrorist movement in 2001 and held the former head of Hamas’ political bureau, Mousa Abu Marzouk, in 1995-97. 

Deif has been wanted by Israel since 1993. He is very secretive and cautious, and has been the target of Israeli assassination attempts, most recently during the Gaza war of 2014. Between 1993 and 2014, he oversaw operations that resulted in the deaths of dozens of Israelis.