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I would make just a few recommendations/revisions on top of the in-game help and official hint guide tactics. I'm not sure how objectively tough the combat was, but I used the tactics below and beat all the training and live scenarios on hard FWIW.

1. Escort is optional: you *can* leave a ship behind to play whack-a-missile for the Lexington, but in most cases you don't have to because you can neutralize a threat and make it back before the Lexington gets too damaged, and she'll auto-repair. I was happier having the extra firepower on offense, but you'll see a couple scenarios where it might make sense to leave a guard.

2. No grouping: the much-vaunted grouping feature is a beautiful lie. As an RTS veteran, this sounded like a no-brainer, but your drone weapons are extremely short range (barely the length of a ship), and when you form a group around a leader, the ships spread out in a wide formation. Once the leader reaches its target, the escorts have to collapse in on it, and by that time, the leader's been ganged up on, and in the face of particularly tight enemy formations your drones will get eaten piecemeal. Instead, slow time to the minimum and just identify the three closest enemy ships and assign three drones directly to each of them. A little micro goes a long way.

3. Maintain the initiative: keep an eye on enemy damage in the right-hand window, and be prepared to quickly switch targets once it's destroyed. When you see the enemy's damage turn red, mouse over the right-hand list or the enemies in the combat window to identify either a) the next adjacent or b) most seriously damaged but not yet targeted enemy. As soon as your first target is destroyed, immediately assign your now-loitering drones to the new target.

4. Attack-Drones only: Fighters are too fragile, and you almost never need Bombers unless you feel like it. Once you clear an enemy capital ship's drones, immediately return your drones for escort/repair. The Lexington has its own shipkillers and can handle the other defenseless ship just fine. Half the time, the enemy cap ship is already dead when your drones are repaired. There's no need to risk a bomber against the other ship's close-in-combat defenses.

5. Combat overview window: you may have noticed that scrolling in the main window is hideous. Most of the time you can avoid it completely by using the combat overview window in the bottom center. Right-click and hold, and move the mouse to pan around the planet; and then left-click and drag windows to zoom. Together, that should eliminate the majority of the need to scroll in the main window.

This isn't comprehensive, but these were the main considerations that got me through the drone missions. Good hunting!