The siege of Charleston during the Civil War began in April 1863 when the Union Navy sent one of the largest fleets ever assembled to attack Fort Sumter. It failed. The Union ironclads proved to be no match for the Confederate artillery. A diversion by Union forces on James Island in July 1863 was the opening scene of the next chapter in the siege of Charleston.

After weeks of secret preparations on Folly Island and Cole’s Island, the Union Army attacked Morris Island at the mouth of Charleston harbor and near Fort Sumter. “We have heavy batteries that have been secretly constructed near the edge of Folly Island,” Capt. Alfred Marple wrote in his wartime diary, “which when they open will surprise the enemy terribly. The prospect seems very fair for our being successful.”

The Morris Island fortifications protected both Fort Sumter and Charleston Harbor. The island was really a sandbar, but in terms of lives, it was an extremely valuable piece of real estate in the summer of 1863. It was to become, in Bruce Catton’s words, “the deadliest sandpit on earth.”

The ultimate goal of the attack on Morris Island was Battery Wagner (called Fort Wagner by the Union Army), a fortification near the tip of Morris Island which commanded part of the island and part of the harbor and the main ship channel.

It was an engineering marvel planned by Charlestonians Captain Francis D. Lee and Langdon Cheves of the Confederate Engineers and originally called the Neck Battery. It was later named Wagner in honor of Lieutenant Colonel Thomas M. Wagner of the First Regiment of South Carolina Artillery, who died from the bursting of a gun at Fort Moultrie in July, 1862.

If Battery Wagner remained in Confederate hands, the Union Army would have no base from which to launch an attack against Charleston. The commanding Union General Quincy A. Gillmore brought in 10,000 more troops and all the cannons and ammunition he could locate.

The Union plan was to move troops from Folly Island to Morris Island, then to Wagner, then to Sumter, and on to Charleston.

On July 10, 1863 most of Morris Island fell within hours. In a brilliant surprise attack led by Brig. Gen. George C. Strong, a Union brigade crossed Lighthouse Inlet between Folly Island and Morris Island. Strong was so anxious to lead the attack that he leapt into water over his head and had to be helped out, losing his boots and hat in the process. The Confederates fought back gallantly but were overwhelmed.

While the initial Union assault was successful, in the end Battery Wagner held. Rowena Reed wrote in “Fighting for Time,” “An enclosed earthwork mounting twelve heavy guns and extending completely across Morris Island near its northern end, Wagner was much more formidable than Gillmore had supposed. Its narrow approaches were protected by rifle pits, mines, and a wet ditch. Constructed of fine quartz sand by Colonel D.B. Harris of the Confederate engineers, with its guns in embrasures and its quarters bomb-proofed, the work was extremely resistant to bombardment.”

Both the fleet and Gillmore’s artillery bombarded Battery Wagner for 11 hours. Confederate Brig. Gen. William B. Taliaferro held Wagner with 1,300 men from North Carolina and South Carolina, including the Charleston Battalion, which fought valiantly.

The direct assault of Battery Wagner itself began 150 years ago on July 10, 1863. The Union plan was to bombard the battery with heavy cannons and then make a direct frontal assault on the fort, which proved to be deceptively strong.

“When I learned what we were to do,” a Union private wrote, “my knees shook so that I thought I should drop.”

At daybreak on July 11, an infantry charge was made up the narrow beach against Wagner. “Aim low and put your trust in God,” General Strong told his lead regiment.

Confederate sharpshooters backed up by expert artillery loosed a hail of fire. There were 339 Union soldiers killed to only 12 Confederates. Gen. Gillmore, the Union commander, should have realized at once that Charleston was not going to surrender easily.

But he did not. Neither did his men.

Capt. Marple wrote his wife, “I feel certain that Gillmore will take Fort Sumter, Wagner and Charleston. He is a live General.”

It was not to be.

Robert N. Rosen, a Charleston attorney, is the author of “A Short History of Charleston” and “Confederate Charleston.” He served as president of the Fort Sumter-Fort Moultrie Historian Trust, which is hosting a presentation on the Battle for Morris Island on July 20, 2013, from 9 a.m.-12:30 p.m. at the Dock Street Theatre.