Lansing's Charlie Company of the First Battalion, 24th Reserve Marines Unit is now activated for duty.
The announcement was made Friday.
100 Marines are based at the Naval and Marine Training Center on East Saginaw Street.
First they will go to Camp Pendleton, California, then they will go overseas in support of Operation Iraqi Freedom.
They will leave within the year, but exact dates have not been set.
Their deployment will last for 12 months.