expression, godan verb (-mu)
group together against a stronger enemy
Idiomatic expression meaning to unite forces to attack a powerful opponent, like a flock of sheep driving a fierce tiger.
弱小国が群羊を駆って猛虎を攻む戦略を取った。
The small nations adopted a strategy of grouping together against the stronger enemy.
The origin is uncertain; the expression uses the imagery of sheep driving a tiger to convey the idea of the weak uniting against the strong.