At the "CO Selection" screen, select Kanebi and any other CO. For the last level, charge up both CO tag power for a fast victory. As soon as you can buy two troops (preferably infantry), do what you must with your starting units (except the black boat, which you should move to the shore). The next day, make sure Kanebi is the second CO and use the tag team power, then move the boat up to the enemy HQ and unload the troops on the shore. You must do this during the first few days before Grimm blocks it off. Next, change CO so that Kanebi is in charge and begin capturing the HQ. Do what you must with the other troop. The next day, Grimm will be unable to damage your troop on the HQ, allowing you to finish capturing the remaining part of the HQ and giving you a fast victory for this level. Remember, this does not work later since Grimm blocks the shores with tanks and stops you from unloading your troops.