What was general sherman's objective on his march to the sea?

To frighten citizens in Georgia so they would give up on the cause of the Confederacy.

General Sherman's "March to the Sea" was a march of a fighting force of around 60,000 men, going from Atlanta to Savannah, Georgia (a distance of 285 miles).  It was intended as a show of force, to intimidate.  They did not burn everything in sight, but did burn the houses and barns of any people who tried to resist them or fight back.