throw down the gauntlet - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Declare or issue a challenge, as in The senator threw down the gauntlet on the abortion issue. This expression alludes to the medieval practice of a knight throwing down his gauntlet, or metal glove, as a challenge to combat. Its figurative use dates from the second half of the 1700s, as does the less frequently heard take up the gauntlet, for accepting a challenge.