drop <target-sub> <dropping-destroyer>
    drop a depth charge on a submarine from a destroyer. If the submarine
    is able, it will fire a torpedo back (which might miss anyway). The two
    must be in the same sector. The mobility drops to 0 with the first
    charge, and by 5 for each additional charge. If there are any others
    subs owned by the same country in range, they will attempt to fire
    torpedoes at you.
Doc: ships, war
Help: torpedo, ships, radar, submarine, destroyer
