Gaza militants resumed their intense bombardment of southern Israel on Monday, with some rockets slipping through Israel’s vaunted Iron Dome defense system and one landing in the yard of a kindergarten. There was no word of casualties, but the second day of violence threatened to unleash a new round of hostilities just a week before Israel heads to elections. Israeli Prime Minister Benjamin Netanyahu threatened Gaza’s Hamas rulers with a “war” if the new round of rocket fire continued, ramping up his rhetoric amid the stretch drive of his campaign.