Ansar Allah began as a revival movement for Yemen's sizeable Zaidi Shiite Muslim sect in the 1990s and began to grow in size and influence through the turn of the century. The group was headed by Abdul-Malik al-Houthi's elder brother, Hussein al-Houthi, until his death at the hands of Yemeni security forces in 2004.

The Iran-backed rebels’ secretive leader had warned Friday that attacks against Israel-linked vessels would resume within four days if Israel didn’t let aid into Gaza. As the deadline passed Tuesday,