Combat 4 is the fourth of the 24 Puzzles in Subterfuge.
Take Control of Garfield.
You can schedule an order to be performed in the future by opening the time machine panel (tap the clock at the bottom of the screen), using the time dial to scrub into the future, and then issuing orders in the same way you would in the present.
You can't launch an attack right now, but you will be able to once the sub arrives at Vaccarino.
To see the solution click Expand below.
Select your 30 driller sub heading to Vaccarino by tapping on it. Tap "Jump to arrival" under the clock icon. Then launch a sub with 21 or more drillers at Garfield.
You can also beat this puzzle by tapping the time machine(clock icon lower left), manually setting it to 8.3 hours and launching a sub from there.