if we didn't go there "for oil",
Until Trump we weren't getting any hug amounts of oil from shale.
America no longer needs foreign oil as America has more oil then any other country in the world.
Back on topic however.
The military personal from Fort Trump would be spending money at the bars and restaurants, buying cars, clothing for off duty, sight seeing tours, Polish girls. airports and pumping money into the local economy like never before.
They would be flying the wives and girlfriends in to stay at the hotels for congenial visits and taking them shopping and on tours.
Hell in a year or two the Polish merchants might even learn what 'customer service' is to triple their profits.