The Israeli military said it sent tanks in to conduct a “targeted raid” in the northern Gaza Strip overnight, describing the brief raid as “part of preparations for the next stages of combat.” It said soldiers “exited the area at the end of the activity.” As calls grow for a cease-fire, Israeli Prime Minister Benjamin Netanyahu said Israel was “preparing for a ground incursion” of Gaza, but that he “won’t specify” when or how it would occur. A U.N. official warned Thursday that, despite Israeli evacuation warnings, “nowhere is safe in Gaza,” with many residents unable to move and facing the threat of airstrikes in the besieged Palestinian territory.