 Banai was appointed to head the Lehi’s combat forces which was renamed under him as the "Fighting Brigade".He masterminded and participated in combat operations such as attacks on military units and police, demolition of bridges, an attempt to free jailed prisoners in Jerusalem that was coordinated with the Irgun, the capture of weapons from a military base in Holon and a British military warehouse on HaYarkon Street in Tel Aviv.Following Shamir’s imprisonment, Banai remained in the underground from where he oversaw all of Lehi’s department’s and branches in Israel.