General Shellby has been grumpy for a hundred and twelve years and sees no reason to stop now. His tanks are slow, his temper is short, and his armour has never, ever been dented. Allegedly.
Shellby's tanks hit 15% harder, so don't trade with them head-on. The usual answers are Rockets, Bomber and Battleship.
Shellby's tanks shrug off 20% of incoming damage: focus fire on one at a time.
All of Shellby's units move 1 less: grab contested properties before they get there.
Finish off Shellby's damaged units before the meter fills: the power heals them back up.
Every hit Shellby's units take fills their power meter, so strike hard in one turn instead of chipping away. When the meter is full, pull fragile units back.