Marwan Issa, deputy commander of Hamas’s military wing and the right-hand man to Deif, is believed to run many of Hamas’s day-to-day operations, said Daniel Byman, a senior fellow at the Center for Strategic and International Studies. With Deif spending much of his life incognito, Issa helps run logistical operations for the al-Qassem Brigades. Israel considers Issa a very significant threat, Byman said.