Fort Wingate:

The Fort isn't too bad of a stage to get through considering the difficulty that was Death Valley. You should have learned by now to stay away from all four borders of the screen. Stay in the middle, shoot 'em down, and you'll surely reach the boss.

At the junction after the series of buildings where the lady merchant is found, you can move to the far right of the screen fooling the programming of the game to hold back the amassed green gunmen.