Most folks walking at a steady pace will do about 3 miles per hour...on a bike it's pretty easy to go 18 or 20 miles per hour...if you want your boys to secure a bridgehead 20 miles inland and don't want 'em to take all day gettin' there, you might want to tell 'em to bring their bikes ! Remember what Confederate General Nathan Bedford Forest said was the key to military victory.."get thar fustest with the mostest." Bikes will help you get thar fustest.
