The Israeli military appears to have encircled Gaza City, but so far, it's made only limited forays into the densest urban areas.
The U.S. has sent military advisers to Israel, including a Marine commander with experience in urban warfare. They'll offer lessons learned and keep Washington in the loop on Israeli moves in Gaza.
The rare daytime arrest operation triggered one of the bloodiest battles in nearly a year of fighting, leaving shops in Nablus riddled with bullets and a building reduced to rubble.
Palestinian militants fired a rocket into southern Israel early Saturday. Hours later, Israeli aircraft carried out a series of airstrikes.