You're hit with a contdown to the Allied invasion right at the start. You need to establish a defendable base and navy quickly. Start pumping out submarines - about 5 in addition to the one you start with should suffice. Make a large mixed force of infantry to protect your base (garrison conscripts in the nearby houses) and build additional war miners when you're capable financially. Once the enemy attack force has been eliminated it's your turn to go on the offensive. You'll need that fleet of subs (maybe even add a couple more, leave a few behind to guard the shores near your base) and some transport ships. Load about 5 transports with rhino tanks, tesla troopers and a couple engineers. Have a sentry gun and tesla reactor ready for when your engineers capture enemy buildings - which you should do now, it's not so hard. Land your transports on the beach to the south of the enemy base, it was poorly defended when I attacked. Make sure you protect your transports with some subs as it really hurts to lose fully loaded transports. If needed once you have control of an area you can build on construct a barracks to reinforce your troops there. Destroy all enemy buildings and you're done.