Donald Sutherland (Oddball) became seriously ill during filming on-location in Yugoslavia. His wife received a telegram telling her to come immediately but warning her that he would probably be dead before she arrived.
The movie was mainly filmed in Yugoslavia because the Yugoslavian army still had a large quantity of Sherman tanks in 1970.
The blue "crosshair" shoulder patch indicates Kelly (Clint Eastwood) and his men are from the 35th Infantry Division. It's a National Guard division, comprised of guardsmen from Missouri, Nebraska, and Kansas.
During filming in Yugoslavia in 1969, Donald Sutherland (Oddball) received word, via co-star Clint Eastwood (Private Kelly), that his then-wife Shirley Douglas was arrested: she had tried to buy--using a personal check--hand grenades from an undercover FBI agent for the Black Panthers. Sutherland recounts this story often, mentioning that when Eastwood got to the part about the personal check, he laughed so hard that he fell to his knees and Sutherland had to help him up. Eastwood then put his arm around Sutherland, walked him down the hill that overlooked the Yugoslavian countryside, and assured his friend of his complete support with his predicament. Sutherland and Douglas, who are the parents of Kiefer Sutherland and twin sister Rachel Sutherland, divorced in 1970.
At the beginning of the movie, Big Joe (Telly Savalas) is desperate to know about the best places to stay in the city of Nancy, and he uses a Michelin tourist guide book. Use of these books by Allied troops during WWII is accurate. When planning the Normandy invasion, staff officers were concerned about how the troops would navigate in light of the possibility that retreating Germans would take down or reverse road signs. The U.S. government quietly reprinted the most recent edition from 1939, as new publications had been suspended because of the war. So when Allied troops stormed the beaches of Normandy on June 6, 1944, they carried the Michelin guides and, for the remainder of the war, advancing forces depended on their Michelin maps.