Following the Confederate defeat at Antietam, the 15th Alabama participated with Jackson's corps at the Battle of Fredericksburg on December 15, 1862. Total casualties there were 1 killed and 34 wounded. The regiment was then reassigned in May 1863 to General James Longstreet's corps, which was then participating in the Siege of Suffolk, Virginia. Here it formed part of the newly created "Alabama Brigade" under Evander Law in General Hood's division, The 15th and lost 4 killed and 18 wounded at Suffolk.