They have taken heavy casualties.

他们遭受了惨重的伤亡。

Heavy casualties were inflicted on the enemy.

敌人遭受了惨重伤亡。

The enemy suffered heavy casualties.

敌人遭受惨重伤亡。

There were heavy casualties in the accident...

那意外事件造成了惨重的伤亡。

They resisted desperately but suffered heavy casualties.

他们拼命抵抗，但还是遭受了严重伤亡。