Filming in Czechoslovakia was interrupted by the Soviet invasion of August 1968. Cast and crew were taken to safety in a convoy of 28 taxis, except for Robert Logan, who stayed behind with film gear in order to capture the invasion on film and photo. According to the book "Bill Collins Presents The Golden Years of Hollywood," a half-replica of the bridge was built near Castelgandolfo, the Pope's summer residence south of Rome, and the film was completed in Hamburg (Germany) and various Italian locations. In 2007, BBC Radio aired "Solo Behind The Iron Curtain" a drama based on the invasion, starring Robert Vaughn as himself.
The producers were granted the right to blow up large parts of the town of Most, but they decided not to blow up the local Communist party headquarters building. Soviet forces were already preparing to invade Czechoslovakia at the time, and the producers didn't want to offend the soon-to-be-arriving Russians.
Some of the jeeps have a vertical bar on the front. This was to cut fine wires set between two trees by the enemy to decapitate the soldiers.
One of the first films to be shot behind the Iron Curtain. Czechoslovakia was seen by Russia as becoming too liberal in its values, and in attempting to justify the forthcoming invasion by the USSR, Soviet agents spread the rumor that the American soldiers in the film were real. Most of them, in fact, were played by Czech students. Pictures of stored movie props were published as "proof" of weapons shipments from the US to arm local "reactionaries". It was even reported that American tanks were rolling through the streets and occupying the towns.
The tanks used by the Americans in the film were M24 Chaffee light tanks. They stood in for five of the newest heavy-duty T26E3 Pershing tanks manned by Company A of the 24th Tank Battalion, although only four were operational on 7 March. The other two platoons were each equipped with five M4A3 Sherman tanks. The command unit consisted of three more Sherman tanks. The Pershings were too heavy for the bridge and were ferried across the river five days after the bridge was captured.