Israel’s military is advancing into southern Gaza in a push that ushers in a new phase of its war against Hamas — and an increasingly perilous situation for Palestinian civilians who have few safe places left to go. New satellite imagery Monday showed dozens of armored vehicles about 1½ miles north of Khan Younis, the largest city in the south. “For people ordered to evacuate, there is nowhere safe to go and very little to survive on,” U.N. Secretary General António Guterres said. Israel says that the Hamas leaders who planned the Oct. 7 attacks are sheltering in the south. “We pursued them in northern Gaza; we are now pursuing them in southern Gaza, too,” an Israeli military spokesman said Monday.