The mission of the STAB was nighttime Waterborne Guard Post duty (WBGP) and daylight troop/SEAL platoon insertion and extraction operations in the Mekong River and Grand Canal areas of South Vietnam.

In August 1969 Admiral Elmo Zumwalt ordered the establishment of Strike Assault Boat Squadron Twenty (STABRON 20) to serve as a fast reaction force and it was formed at Mare Island Naval Shipyard.

[1][2] The first shipment of 14 STABs arrived at their operational base, the USS Benewah near An Long on 27 February 1970.

Two additional STABs arrived into South Vietnam on 9 March and were transported to the base on USS Benewah.

An inspection of the STAB found that one B-40 penetrated near the waterline and exploded next to a fuel bladder which self-sealed, while an apparent recoilless rifle hit severed the control cables rendering one engine inoperable.