If there's a lot of shield fuel and repair commodities on the base it can take 10 or 20 or 30 battleships pounding on a base to do any reasonable damage. The shield keeps out most of it. 5 battleships or so don't have a chance of doing more damage than is repaired. So if there is a lot of repair commodities and shield fuel, it's going to take a whole lot to take a base down. And bases do 3 checks every tick per upgrade level. So a level 4 base will repair 12 times each tick. You might want to bring an armada or three
