cross the Rubicon

cross the Rubicon (formal)

to do something which will have very important results, which cannot be changed later. International pressure may be able to prevent the country crossing the Rubicon to authoritarian rule.

See also: cross

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cross the Rubicon

to make a decision that cannot be changed later. When I quit editing and decided to be a writer, I had crossed the Rubicon to an uncertain future.

Etymology: based on Julius Caesar's crossing of the Rubicon River in 49 B.C.E., which began a war

See also: cross