declare war on

Idioms  

1. Also, declare war against. Announce one's intent to suppress or eradicate something or someone. For example, The police have declared war on drug dealing in the neighborhood, or Several gangs have declared war against each other. This usage transfers the literal sense of the term, “to state formally one's intention to carry on hostilities against another power,” to a somewhat smaller scale.

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Example Sentences

The attack on the base, as well as similar attacks in the Philippines and Guam, spurred the United States to declare war on Japan.

From Salon • Mar. 19, 2026

This week saw Roman Catholic cardinals meet to choose the next pope, people across Europe mark the 80th anniversary of the end of World War Two, and Donald Trump declare war on foreign films.

From BBC • May 8, 2025

The attacks prompted Mr. Netanyahu to declare war on the militant group.

From Washington Times • Oct. 7, 2023

Those of a certain personality declare war on their own vulnerabilities, as my father did, fighting to hold onto his dignity.

From Los Angeles Times • Apr. 29, 2023

Three days later, the world spins wildly again when the British and the French honor their promise to Poland and declare war on Germany.

From "The Boy Who Dared" by Susan Campbell Bartoletti