According to Sears in his book "Chancellorsville" he comments that up until the spring of 1863 the Union Army had not kept records on why a soldier was absent from his post. That deserters were not listed as a seperate classification from soldiers who were absent on leave, or on furlough at home for wounds.

In the first muster in which they began listing a reason for these absences there were over 85,000 men missing from the ranks of the Army of the Potomac of which over 25,000 were listed as "deserters". That was the reason for Lincolns amensty. It was also the reason for the Union Conscript Act as the numbers of union troops were falling and the expiration date of the 2 year and 9 month enlistments was fast approaching before the spring offensive began.