Union Navy fails to fight past Drewry's Bluff below Richmond in May 1862.
Nowhere did Matthew Fontaine Maury best deliver his service in coastal defense to the Confederacy than at Richmond during the Peninsula campaign. His torpedoes [mines] and coastal batteries ultimately forced the Union to keep to the land as its soldiers drew closer and closer to the capital. He had made the river a death trap for the Union Navy. The few poor roads, thick woods, and swamps to the east proved natural chokepoints and lines of defense. The fortuitous finding of miles of insulated telegraph cable along Willoughby Spit in Hampton Roads in February 1862 allowed Maury, not President Jefferson Davis or Navy Secretary Stephen Mallory, to make the James River near the capital impenetrable by the summer of 1862, indeed for the remainder of the war. While the press clamored for stout defenses, Maury quietly provided them.
About six miles downstream of Rocketts Wharf, the Confederate Navy’s shipyard, Maury and his assistants, notably Hunter Davidson, like Robert Minor and John Mercer Brooke, a member of the Naval Academy’s first graduating class with service at the observatory, set their mines in the narrowest and shallowest part of the river. They placed the mines in mid-channel at between three and a half and seven and a half fathoms of water.
The place for the "ranges” selected was under the cover of the guns on Drewry's Bluff on the south bank and Chaffin's farm on the north. "They were ignited by a bit of fine, platinum wire, heated by means of a galvanic current from a galvanic battery on shore. The conducting wire having been cut the two terminals were then connected with the platinum wire making a span between the terminals of say one-half inch. They were then secured firmly in a small bag of rifle powder to serve as a bursting charge,” Maury later reported.
By June 1862, Maury and Davidson, who had served aboard CSS Virginia, had fifteen casks in the river, arranged in rows and spaced about thirty feet apart. They transformed Samuel Colt’s minefield concept from an art to a science. The Confederates in Richmond were making “submarine warfare an extremely important and feared tool of war.” Again, Maury relied on stealth to hold off nosy Union gunboat commanders. If the Navy or Virginia Governor John Letcher had more powder, Maury and Davidson would have deployed more mines.
The Union Navy on the James River and in Hampton Roads wanted Maury’s plans for river defense. With them, they would know the “ranges” of torpedoes, sunken vessels, and other obstructions, and the large gun emplacements. They reasoned snipers from the shore would be a manageable risk. This summer, they were living in the shadow of Captain David Glasgow Farragut’s daring rush up the Mississippi River with his ocean-going frigates and sloops that led to the fall of the South’s largest city and busiest port, New Orleans.
Even after the Battle of the Ironclads in Hampton Roads, Union Navy officers in the East, unlike their Army counterparts, were used to having their way. Cape Hatteras, Port Royal, Roanoke Island, and New Bern kept hopes for a short, victorious war. But now, they were constantly being stymied. The ironclads were not enough to force the Union Navy’s way to attack the city and the Army of Potomac for now was operating too far north of the river for their guns to offer support.