Once the Union battery at Venus Point was disclosed, Confederate gunboats engaged in gunnery duels, but they were driven off. Over the next week, the besiegers completely surrounded the Fort. Federals built another battery on the Savannah River across from Venus Point. They threw a boom across Tybee Creek and cut the telegraph line between Savannah and Cockspur Island. Two infantry companies entrenched nearby to ward off Confederate raiding activity and a gunboat was detailed to patrol the channel and support the infantry. By late February 1862, no supplies or reinforcements could get in; the Confederate garrison could not get out. The last link of communications was a weekly swamp swimming courier.