Read the excerpt from The Dark Game: True Spy Stories from Invisible Ink to CIA Moles.There are theories as to why the Soviets did not "discover” the tunnel sooner. One likely answer is that they waited until Blake was reassigned by MI6 to London in order to protect him from being found out. Since Blake knew about the tunnel from the first day of its planning and was in Berlin while the tunnel was being dug, fingers would soon point to him as a Soviet mole. The KGB did not want to lose Blake. Some historians feel that the KGB waited because they actually wanted the Americans to hear their transmissions, as a way to let it be known that Russia had no intention of invading Germany and going to war with the U.S.On balance, however, some valuable information was gathered from the tapped conversations. The U.S. learned, for example, a great deal about the Soviet and Eastern European order of battle, or its military organization. Others feel that the intelligence was valuable to check against similar information obtained from other sources. Tim Weiner in his recent history of the CIA, Legacy of Ashes, writes that "The evidence suggests that the CIA gained two invaluable and untainted kinds of knowledge from the taps. The agency learned a basic blueprint of the Soviet and East German security systems, and it never picked up a glimmer of warning that Moscow intended to go to war.”