In August 1968, Soviet forces invaded their captive ally Czechoslovakia. The invasion began with an intense electronic warfare campaign against the Czech air defense network. A declassified secret US Defense Intelligence Agency report, titled “Soviet Electronic Countermeasures During Invasion of Czechoslovakia” and produced in October 1968, provided substantial detail on Soviet electronic warfare actions. It stated, “Electronic countermeasure activity was concentrated southeast and east of Prague to screen and protect Soviet air movements.” It added, “Jamming apparently was not targeted in the radio frequency range of NATO radars; the locations of chaff seeding suggests that it was not intended to...