When, after almost a month of backbreaking labor, David Farragut finally succeeded in getting his heavy deep-sea ships inside the mouth of the Mississippi River on 16 April, he ordered the mortar flotilla to commence operations.

Porter's ships, camouflaged with bushes and tree branches, moved up river to pre-assigned positions below Forts Jackson and St. Philip and opened fire 18 April.

During the ensuing 6-day bombardment, Horace Beals kept the mortar schooners supplied with ammunition and provisions, took on board ordnance and other stores, and embarked and cared for sick and wounded from ships of the squadron.

The Confederates had cleverly placed these guns high on the bluffs of the Chickasaw Hills perfectly safe from the low trajectory cannon mounted on the Union's salt-water ships.

After withdrawing from the Mississippi River with Admiral Farragut, Horace Beals spent the rest of the year supplying ships of the West Gulf Blockading Squadron, operating from Pensacola, Florida, as a base.