The Soviets left troops in Cuba purportedly to keep control of the launch capability. The story I remember was that the soccer fields constructed for the Soviet troops was what alerted the U.S. to take a closer look.
It makes me wonder about the stadium China is building for Costa Rica (in San Jose, next to La Sabana park). They're nearly finished building it, all with Chinese labor. All materials, equipment, even the food for the workers is brought in from China.
It's a completely "no strings attached" gift from China to Costa Rica.