Also, hard on the heels of. Directly behind, immediately following, as in Mom's birthday comes on the heels of Mother's Day, or Hard on the heels of the flood there was a tornado. The hard in the variant acts as an intensifier, giving it the sense of “close on the heels of”. [Early 1800s] Also see at one's heels.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.