No, you don't have to enlist to fight. These "volunteers" will serve a different purpose.
A different army of volunteers will soon descend on America's Civil War battlefields -- only this horde of dedicated men and women will be armed with paint brushes, trash bags and weed whackers. This "battle" is called Park Day. The volunteers will be battling the ravages of Mother Nature plus heavy usage by mankind: the volunteers will be sprucing up the historic sites and making them into something that all Americans can be proud of.
Park Day occurs at most participating sites on Saturday, April 1, 2006, although some sites prefer to have their events later in April or in early May (please check the complete list of participating sites for the exact local Park Day dates).
Last year, the winner of the most active Park Day participating site was Raymond Battlefield, Mississippi. Among the items removed from the site were a refrigerator, a washing machine, mattresses, and lots and lots of trash!
You can see the current list of participating sites at http://www.civilwar.org/parkday