Lebanon’s Hezbollah vowed on Monday to quickly choose a successor to killed leader Hassan Nasrallah, and to continue the Islamist militia’s decades-long fight against Israel. Deputy head Naim Kassem, in a televised speech, said the group will choose a successor for Nasrallah to assume the secretary general position “as soon as possible.” He said that the group’s structure allows it to find replacements for all senior members, as they already have deputies and qualified members. “We know the battle could be long, and we are ready for any possibility. If Israel decides to launch a ground invasio…