From Longman Dictionary of Contemporary Englishbe at daggers drawnbe at daggers drawnANGRYif two people are at daggers drawn, they are extremely angry with each other → dagger
Examples from the Corpus
be at daggers drawn• The prospect of an interesting friendship had been destroyed and now they were at daggers drawn.• In practice they are at daggers drawn as the furore over Tom Clarke's pronouncements on the subject this week amply illustrates. 