Suck it up, rub some dirt on it, and move on.

If he keeps it up, dedicate your entire set to ruining his. Understand that you are not going to get immediate gratification here. Drop any credit card mentality at the door. You are outmatched at the moment. You cannot get satisfaction right now.

Plan, scheme, prepare. Your country is set up too weak if someone is grabbing you with ease and there is literally not a thing you can do about it. You will not
be winning, placing well, or advancing with a weak country. Accept this fact at the moment, and be pleasantly surprised if later your country is stronger.

Start building spies. Get missile tech. Get tanks. Be able to get a spy op on him. Scheme and prepare for when you can hurt him. A month is a long time. If your finish is already ruined, return the favor before the set is out.

I start scheming in the first half of the set about which land grabber I am going to "party" with at the end. Doesn't mean I am going to, but I am ready and prepared.

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Or the guy may just never hit you again. Suck it up, rub some dirt on it, move on, and wait for the next guy to triple tap you. Your country needs to be stronger.