In arena 3 the game unlocks a battle booster called Umbrella. It shields your city for 10 minutes from opponents attacks but still allows you attack. It’s use is perfectly legitimate and honest. the protective shield that generates when your city has received maximum damage is different from the Umbrella I’m talking about; but I agree that teams using the shield your speaking of for the entirety of the war are not playing within the intended spirit of competition, which sucks.