Read the excerpt from The Dark Game.
Tension between the two sides escalated until June 1948, when the Soviets blocked all western access to the capital. In this first real crisis of the Cold War, the West was not going to be denied by the Soviets. Since such tension was typical in the divided city, it should come as no surprise that Berlin in the early 1950s was a city of intrigue, espionage, and danger.
Which term means "spying"?

tension
escalated
divided
espionage​