Star Fox 2/Walkthrough

Star Wolf
Pigma, Leon, and (on Hard and Expert) Andrew will each be at a planet. You can see them on the map as they will be represented by twinkling stars. If you attempt to enter a planet they're sitting on, you will have to fight them first. After a while, they will leave their planets to seek and destroy you. These guys can be a real pain on Expert mode, since they have high shields and they repel your attacks pretty well. You will also encounter Wolf once you have destroyed all the battleships and bases, and he's tougher than his comrades. It may be easiest to take them down with nova bombs, but they will sometimes avoid them, too.

Strategy
Other than to destroy battleships and bases without dying, you also must keep Corneria from taking damage. Any damage inflicted is permanent, and you will lose the game if Corneria reaches 100% damage. Damage can be caused by enemy squadrons, IPBMs, battleships firing the Planet Cannon (you'll know it when this is about to happen), and the satellite system firing upon Corneria. The satellite system is normally your friend and it will take out enemies on the map, but if it gets infected with a virus, it will fire upon Corneria instead. You can rectify this situation by going to the satellite and removing the viruses.

IPBMs will explode upon impact, causing significant damage. On the other hand, enemy squadrons will remain on top of Corneria and keep attacking. This makes them more of a threat, but they seem to not take so direct a route to Corneria as IPBMs do.

On Normal and Hard there's not much strategy involved: just take down missiles and squadrons when you see them, and if there are none, take down a battleship or a base. Give battleships a higher priority on Hard mode because they are equipped with Planet Cannons that can damage Corneria. It's no big deal, though; it's likely Corneria will not suffer serious harm.

On Expert mode, this strategy will not work. If you keep destroying every enemy you see on the map before taking on a base or a battleship, you will simply get overwhelmed and if you keep using this strategy to the end, Corneria will fall. Andross will very often screw you over once you get rid of that last IPBM on the map, for instance by ordering battleships to advance to Corneria and fire the Planet Cannon while launching an IPBM from every base.

The key is to be aggressive and take down battleships and bases quickly. Although Corneria may take some damage at first, Andross' capacity to cause future harm will be reduced. In other words, you're taking a short-term risk for a long-term gain. By no means should you ignore enemies that are near Corneria, and if there are several enemies on the map, you should take out those closest to you. However, if there's a lone enemy on right side or even near the middle of the map, you might to well to just take out a battleship (or if there are no battleships, a base). If there's just one enemy and the satellite system is fully charged, you can probably ignore the enemy entirely unless it's extremely close to Corneria. It would take a lot of luck and skill to beat Expert mode without Corneria getting hit, so don't worry too much about it unless the situation truly becomes alarming (but if, for example, you get over 50% damage and most of the enemy bases are still there, you're probably doing something wrong).

When you start liberating planets, take Meteor first. It's in the center of the map, which is a great location for your mothership since it will never be too distant. The order of the other planets is not too important, but it may be wise to take out bases nearer Corneria first, since it will be easier to intercept IPBMs launched from distant bases.