Israeli Prime Minister Benjamin Netanyahu said “we are at war, and we will win it” as the country’s air force began striking Hamas targets in Gaza on Saturday, in response to a surprise assault on the 50th anniversary of the start of the 1973 Yom Kippur war. Hamas militants infiltrated Israeli territory from the Gaza Strip — including by paraglider and over the sea — and launched more than 2,200 rockets, Israeli military leaders said. The confrontation, which has killed at least 20 Israelis and injured at least 545, is one of the most serious in years following weeks of rising tensions along the volatile border. In a rare statement, Hamas military commander Mohammed Deif called on Palestinians inside Israel and Israel’s Arab neighbors to join the fight.