Yahya Ibrahim Hassan Sinwar was a prominent Palestinian militant and political leader who served as the leader of Hamas in the Gaza Strip from February 2017 until his death in October 2024, making him the de facto ruler of the territory during that period. Born on October 29, 1962, in the Khan Yunis refugee camp in the southern Gaza Strip, he grew up in a family displaced during the 1948 Arab-Israeli War. Sinwar became involved with Hamas in the late 1980s, co-founding its security apparatus, the Majd. He was arrested by Israeli authorities in 1988 and sentenced to four life terms for his involvement in the kidnapping and killing of Israeli soldiers and civilians. After spending 22 years in Israeli prisons, where he learned Hebrew and studied Israeli society, he was released in 2011 as part of the Gilad Shalit prisoner exchange deal. Sinwar quickly rose through Hamas ranks, becoming the de facto leader in Gaza in 2017. Under his leadership, Hamas intensified military operations against Israel, including overseeing rocket attacks, constructing extensive tunnel networks, and orchestrating attacks such as the October 7, 2023, assault on Israel that killed around 1,200 people and led to the abduction of over 250 hostages, for which he was a key mastermind. In August 2024, he was appointed chairman of the Hamas Political Bureau, becoming the organization's overall leader. Designated as a terrorist by Israel, the United States, the European Union, and multiple other governments, Sinwar was targeted in multiple Israel Defense Forces (IDF) operations and evaded capture for over a year during Israel's military campaign in Gaza before being killed on October 16, 2024, in a clash with the IDF in Rafah, southern Gaza.