← The Soviet-Led Invasion of Czechoslovakia, 1968

Soviet denial and deception materially shaped the Western assessment.

contestedconfidence: moderate

Argued in CIA's own Studies in Intelligence, but the same article records that the troop movements were in fact observed and promptly reported.

Supporting and corroborating evidence

Some analysts believe that the USSR conducted a deliberate and fairly successful political and military deception campaign…which was intended to conceal the scale and purpose of the military movements, and to deceive the Czechoslovaks and others into believing that there would not be an invasion.

Cynthia M. Grabo — CIA-CSI-GRABO-14-1, CIA Center for the Study of Intelligence, 1970-01-01 · source ↗

Contradicting evidence

There were any number of observations by Western sources of the Soviet troops along the Czechoslovak border, and the start of the massive movement into Poland in late July of troops from the Baltic and Belorussian Military Districts was fortuitously witnessed and promptly reported to the US Embassy by several US tourists and other travelers.

Cynthia M. Grabo — CIA-CSI-GRABO-14-1, CIA Center for the Study of Intelligence, 1970-01-01 · source ↗

Context

Dubcek regime can take considerable credit for saving its skin at Cierna and for staring down the Soviet threat of force.

Jacob Beam — FRUS 1964-68 v17 D77, Embassy Prague, 1968-08-04 · source ↗