expression
die together; go down together
Idiomatic expression meaning to share the same fate, especially in death or destruction. Often used in dramatic or literary contexts.
敵艦に体当たりして、死なばもろともと突っ込んだ。
They rammed the enemy ship, charging in with the resolve to die together.
彼は「死なばもろとも」と叫んで、崖から飛び降りた。
He shouted 'If we die, we die together!' and jumped off the cliff.
From classical Japanese conditional 死なば (if [one] dies) + もろとも (together). The phrase is a fixed idiomatic expression.