all's fair in love and war

all's fair in love and war idiom
Any conduct is permissible in certain circumstances, as in Of course he called her—all's fair in love and war. This maxim, stated in various forms from 1579 on, today sometimes appears altered by an addition or substitution, as in All's fair in love and the World Series, or All's fair in love and war and an election year.

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.

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