Battle of Spanish Fort
Maj. Gen. E.R.S. Canby’s XIII and XVI corps moved along the eastern shore of Mobile Bay forcing the Confederates back into their defenses. Union forces then concentrated on Spanish Fort and Fort Blakely. On March 27, 1865, Canby’s forces rendezvoused at Danley’s Ferry and immediately undertook a siege of Spanish Fort. The Union had enveloped the fort by April 1, and on April 8 captured it. Most of the Confederate forces, under the command of Brig. Gen. Randall L. Gibson, escaped and fled to Mobile, but Spanish Fort was no longer a threat. 
Siege of Spanish Fort
Delays in the march and efforts to unify his entire force required Canby to remain on the Fish River for longer than expected. The Confederate defenders used the hesitation to make some moves of their own. On March 23rd the 16th Confederate Cavalry, commanded by COL Philip Spence,moved out from the fortifications followed by the 32nd and 58th Alabama Infantry. While the Confederate troopers trotted forward to scout the Union strength at Fish river the two regiments of Alabamans established a position at Hollywood. The next morning, BG Randall Gibson's brigade of Louisiana Infantry, fortified with artillery support, moved about eight miles south of Spanish Fort. At D'Olieve's Creek they threw up breastworks in anticipation of contact with the lead Union elements moving north. BG Francis Cockrell's Division also moved out of the fortifications and occupied a blocking position at Alexis Spring.
The first contact was made by Spence's troopers, who engaged COL Henry Bertrams brigade, who were in the van of the Union advance. Spence incorrectly identified the size of Bertram's force as a division creating confusion in the Confederate headquarters. This poor estimate coupled with other intelligence gathering errors about Union strength on the eastern shore of the bay gave the overall Confederate commander there, BG St. John Liddell, a totally inaccurate picture of the Union forces that opposed him. He continued to believe that only MG Gordon Granger's XIII Corps troops were in his front and these were badly divided. His original plan called for the forward deployed troops (Gibson and Cockrell) to stall the advance while BG James Holtzclaw's brigade would manuever for an attack on the Union right flank.
On March 25th, Liddel finally learned that MG Andrew Smith's XVI Corps was not only present but had already flanked his line on the left.His units were now dangerously exposed to the possibility of becoming cut off and destroyed in detail by the much larger Federal force. He immediately abandoned any thought of engaging the Union forces and ordered his troops back into the fortifications. Cockrell retired to Fort Blakely and Gibson to Spanish Fort.
Spanish Fort consisted of a line of field fortifications and batteries near where the Apalachee River emptied into the bay. Behind the mile and a half of works stood Old Spanish Fort, Fort McDermott, and Red Fort. The garrison there now numbered about 3,400 soldiers commanded by BG Gibson. They had spent considerable effort improving the defenses by incorporating detached rifle pits in front of every battery, an abatis only 50 feet from the main breastworks, and a ditch 5 feet deep and eight feet wide. There were about forty artillery pieces in the fort and the threat that the landscape in front of the fort had been laced with "sub terra" shells. Although Canby's forces numbered about 20,000 in front of Spanish Fort he expected a serious fight.
While Forrest was meeting defeat around Selma MG Canby was encouraging the Union navy to move up the river to seal off the rear of the Confederates at Spanish Fort. Two gunboats (Octorara and Genesee) and four monitors (Kickapoo, Milwaukee, Winnebago, and Chickasaw) attempted to pass over the Blakely Bar on March 28th. The Octorara grounded almost immediately in eight feet of water and burst a steam tube in the futile effort to work her way free. The Winnebago and Chickasaw managed to clear the obstacle but the elevation restrictions on their guns would not let them take the fort under fire. On the trip back down stream the Milwaukee was sunk by a mine. The next day the Osage was a sunk in the same fashion, despite efforts to clear a channel in the shallow water. On April 1st the stern wheeler tin-clad Rodolph, manuevering to raise the sunken Milwaukee was also sunk by a mine. The water depth and threat of mines prevented further naval involvement at Spanish Fort. It was a lack that paid great dividends for the Confederates defending the fort.
The Union infantry had been moving into position to assault the fort since March 27th. BG Eugene Carr's 3rd Division of the XVI Corps moved within four miles of the fort before the 21st Alabama ambushed the 81st Illinois causing a temporary delay of the Federal advance. The 124th Illinois moved up and pushed the Confederates back until Carr was within a mile of the fortifications. BG John McArthur's 1st Division assumed a position on his left joining the two Federal corps (XIII and XVI) in a total investment of the fort. BG Kenner Garrard's 2nd Division was used to protect the rear and right of the army.
Continued forward movement pushed the Union lines to within 400 yards in expectation of the final assault order. An effort to soften the defenses with a bombardment with organic artillery assets (3rd Indiana Light and 2nd Iowa Light) but the Rodmans and Napoleons did little damage other than wounding one Minnesota soldier and pinning down the most forward deployed Union units. MG Andrew Smith requested permission to conduct the assault on the works but when Canby asked division commander McArthur his opinion he replied that he would lose half his men in the effort. Canby thought better of the request and refused to issue the go ahead.
The XIII Corps troops on the right took matters into their own hands. MG Gordon Granger ordered a push by the 20th Wisconsin and 19th Iowa. LTC John Bruce of the 19th Iowa "advanced companies A and D in a skirmish line through thick brush" but a spirited resistance along the line stopped any sustained effort. Granger's troops suffered 77 casualties. These coupled with the 91 casualties suffered by Smith's corps in operations earlier in the day convinced Canby to approach the stronghold more carefully. Shovels replaced muskets and the seige of Spanish Fort began. BG Carr reported that after the efforts of the 27th his command was "incessantly occupied making approaches, parallels. and batteries." The attention of the commanding general fell to the logisitical support of his force while they dug their way closer to the enemy works. Canby ordered "the engineer trains and material" forward and a depot was established at Starke's Landing when "wharves were built, roads opened, and the supply of the army secured."
The digging continued for days, interrupted by ocasional outbreaks of firing between Confedertae skirmishers and Union forces advancing on their works. The action was typified by exchanges between the most forward parties on both sides. On March 31st members of the 7th Vermont began digging rifle pits within 150 yards of Slocomb's Confederate battery. The new position was close enough to allow Union marksmen to kill the Confederate artillery chief, COL William Burnet. In retaliation the batteries opened on the Vermonters driving them into a ravine for protection. When the fire abated CPT Riley Stearns led his men back into the forward positions to harass the enemy gunners. Undaunted, the Confederates tried another tactic to rid themselves of the pesky riflemen. They set fire to the slashings in front of their positions in an attempt to smoke the Vermonters from their holes. When CPT Riley Stearns ordered a retreat the first few men to attempt the dash back were cut down by Confederate rifle fire. Reacting, Stearn's detachment hunkered down in their holes and weathered another artillery barrage . The smoke from the fire and the artillery fire covered CPT Clement Watson and 31 Confederate infantrymen who descended unseen to capture Stearns and his 21 man party.
Despite the setback the progress of the Union works went unchecked. As they inched closer Canby ordered BG James Totten to bring his seige train up to assist with the effort. Totten brought the big guns up from Dauphin Island and landed them at the new wharf at Starke's Landing. They were deployed around the fort and began pummeling the fort from ever decreasing range. MG Maury, possibly anticipating a negative outcome at Spanish Fort, began ordering troops out of the fortifications. When he sent word that Ector's Brigade was to move to Fort Blakely Gibson could not believe the order and questioned Maury, The reply was a simple "Ector's Brigade must come up."
As Ector's Brigade prepared to depart Gibson was left with about 2200 defenders. Seeing the eventual outcome Gibson used the failure of the Union Navy to seal the rear of his position to construct a treadway across the swamp at the rear of the fort. The 18 inch walkway grew to over 1200 yards long and Maury knew that it would provide the only escape route when the inevitable assault came.
On April 8th Canby decided that the time had cometo make his move. As the concentrated weight of fire from 96 Federal guns pounded the fort a general advance was ordered. On the extreme right of the line the 8th Iowa almost immediattely gained access to an area of the fortifications known as Red Fort. As they moved down the line, reinforced by the 81st Illinois, 108th Illinois, and 124th Illinois, the brief fight turned into a rout. In the center the 19th, 8th, and 23rd Iowa also gained the works but were slowed by a counter attack by COL David Coleman's North Carolinians. The attack was repulsed but gained enough time for the wholesale evacuation of the fort to begin. Roughly three quarters of the garrison escaped using the treadway through the swamp. Canby was left with the fort, about 500 prisoners, 50 spiked artillery pieces, and the munitions and supplies in the fort. The escaped Confederates joined the garrison at Fort Blakely.