Defense Secretary Lloyd Austin warned Saturday that Israel must protect Gaza’s civilian population. “And if you drive them into the arms of the enemy, you replace a tactical victory with a strategic defeat,” Austin said. He made the comments the same day Gaza health officials said the death toll in the territory surpassed 15,000, and as Israel ramped up airstrikes after a seven-day pause in fighting with Hamas. The head of Israel’s Mossad intelligence agency told its delegation to return from Qatar, which mediated talks over the pause, after an “impasse,” Israeli Prime Minister Benjamin Netanyahu’s office announced Saturday. The Israeli military said it was “preparing for the next stage — southern Gaza,” adding that warplanes hit more than 50 targets in the Khan Younis area.