This volume, the fourth in the series, covers the final year of the Marine Corps' experience in the Civil War. The year opens with the elevation of Major Jacob Zeilen to the commandant of the corps, over those officers senior to him, thus ending the policy of accession to that post by seniority and establishing the precedent of deep-selection. The battle history of the corps continues, with a complete account of the marines in the desperate fights at Mobile Bay, Honey Hill, Tulifinney Crossroads, and Fort Fisher being recounted for the first time. With the fully detailed story of the marines at the Battle of Fort Fisher, the long held belief that they were responsible for the failure of Rear Admiral David D. Porter's sailors to capture the Confederate works is discredited. Active on all fronts to the end of the war, marines also played a little-known role in the events surrounding the assassination of Abraham Lincoln. Concluding the work is a detailed refutation of the spurious, erroneous, and often derogatory conclusions that have become part of the historical record of the Civil War.