CAIRO (Reuters) -A greatly weakened Hamas has sought to reassert itself in Gaza since a ceasefire took hold, killing dozens of people in a crackdown on groups that have tested its grip and appearing to get a U.S. nod to temporarily police the shattered enclave. Pummelled by Israel during the war ignited by the October 7, 2023 attacks, Hamas has gradually sent its men back into the streets of Gaza since the ceasefire began on Friday, moving cautiously in case it suddenly collapses, according to two security sources in the territory. On Monday, Hamas deployed members of its Qassam Brigades military wing as it freed the last living hostages seized two years ago.