declare war against (someone or something)

declare war against (someone or something)

1. To officially announce the intention to fight against an enemy country or group in a war. We will have to declare war against the rebels if they advance over our border.

2. To announce the intention to vehemently oppose someone or something. This usage does not refer to physical fighting. The mayor has declared war on crime in our city and is bolstering our police force.

See also: declare, war

Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

declare war against someone or something

 and declare war on someone or something 

1. Lit. to formally announce that one will fight a war with someone or some country. A group of countries declared war against the aggressor.

2. . Fig. to announce a serious campaign against a type of person or a serious problem. The president declared war against crime and criminals. The pressure group declared war on waste.

See also: declare, war

McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.