How do you delete your own units once you have got them?

I don't think you can destroy units
Wonce built

Play nuclear war mode if you have the ad on

The only way to delete them is to send them to their doom! Match your individual units against an enemy that is sure to destroy them. You have to give up points to your enemy, but it's an effective method of changing your strategy mid-game.

Well, wasting troops by sending them to their doom is not a good idea, instead... You could keep the troops you don't need for your new plan or whatever, you could just keep them in reserve until they are needed, or use them for commando raids or false attacks or send them to support your ally... But you would need some form of mobile base defence so keeping them in reserve is the best option, I myself did a mission, and I had heavy units so I used them to assist my ally and push the enemy back, I had to use my weaker troops as a reserve army that would help the main defense force guarding my HQ, the Italians tried to attack on what looked like a weak defense... Which was a failure, because I had reserve troops, I was more capable of defending my base and attacking on another area, so reserve troops would the wisest and most logical strategic choice for multiple defense battles and offensive battles, etc. It is far more wise to have reserve, I suggest you use this to your advantage.