！
We've destroyed the enemy flagship!
Literal
Enemy [possessive-の] flagship [object-を] destroyed!
旗艦 'flagship' — 旗 'flag' + 艦 'warship.' 撃破 'destruction (in battle)' — 撃 'strike' + 破 'break.' The ました ending is polite — a military report to a superior. Short, punchy combat reporting.