act of war

American  

noun

1. an act of aggression by a country against another with which it is nominally at peace.

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act of war British  

noun

1. an aggressive act, usually employing military force, which constitutes an immediate threat to peace

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Example Sentences

After a ceasefire, Modi vowed that "any attack on Indian soil will be considered as an act of war".

From Barron's

This was nothing less than an invasion, Khrushchev charged, an act of war.

From Literature

A blockade, like an air strike, was an act of war.

From Literature

In the end, it was an act of war that set the stage for an ambitious plan to end the conflict once and for all.

From The Wall Street Journal

Since a blockade is an act of war against an enemy state, China would call its action something else, such as a quarantine.

From The Wall Street Journal