After the Union decides to allow blacks to fight on their side, what position does Douglass assume?

recruiting African American soldiers into the Union Army and actively participated and initiated recruitment meetings.

Explanation:

After the declaration of Emancipation Proclamation by President Lincoln, slaves from Confederate states became free and were allowed serve in the Union army. Frederick Douglas who had been suggesting President Lincoln for the recruitment of slaves in the Union army finally achieved his goals.

Douglass assumed the role of recruiting African American soldiers into the Union Army and actively participated and initiated recruitment meetings and events in different parts of the country.