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3. declare war against

declare war against

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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