Factual error: In one scene of the film, Rommel is shown wearing a swastika pin. Rommel was not a member of the Nazi party and refused to wear any Nazi insignia (outside of uniform symbols which contained it), instead he wore the traditional Prussian Iron Cross.
Factual error: Despite it being the most common American tank of the war by far, the only M4 Shermans seen in the film are in archive footage. None are seen in action at all. Most of the American tanks appear to be M47 Pattons, which didn't enter service until 1952.
Factual error: At the beginning of the movie, Patton is reviewing Morrocan troops during a formal parade. This includes a scene of camel mounted soldiers at attention lined up side by side. These soldiers are armed with the French MAT 49 submachine gun. This weapon was first manufactured in 1949, several years after World War Two had ended.
Continuity mistake: When the three small boys run up and salute Patton, the middle boy stops with the other two slightly behind him to each side, and is the first to salute. When the camera angle changes to view them from in front, the middle boy is instantly behind the other two, and is the last to salute.
Factual error: When Patton is given command of Third Army in France in 1944, he says that the assassination attempt on Hitler took place several days ago. Later on we see Field Marshal Rommel in a German command HQ looking quite healthy. Rommel was actually severely wounded three days prior to the attempt on Hitler and was in the hospital.
Continuity mistake: In the scene before Patton hears the news of getting relieved of command, he is walking with his NCO aide George, who is wearing E6 rank on his shirt. In the following scene while getting ready for bed, the same sergeant is now wearing E5 rank.
Factual error: In a scene set in 1944 France, shortly after D-Day, Patton is riding in a very distinctive type of Jeep that first went into production in 1953. Another Jeep in that same scene dates from 1950 onwards.
Other mistake: During the early part of the movie, when Patton is in Morocco, you can see two kids visibly mugging for the camera as they do cutaways on two distinct occasions.
Factual error: The drum major leading the British pipes and drums into Messina is a corporal wearing the usual two point-down chevrons on his upper arm. British Army drum majors, who all hold a minimum rank of sergeant, wear four point-up chevrons on their lower arm (on a leather strap if in shirt-sleeve order).
Continuity mistake: When the two Jeeps arrive at the Kasserine Pass to survey the results of the battle, the second Jeep comes to stop just short of running over a dead soldier. At the end of the scene, the same Jeep drives away, going forward as if to run over that body, but the body has vanished.
Factual error: During the early portions of the film, General Bradley's Jeep is a proper WWII Willys Jeep Model MB (wipers on top of windshield), but the second Jeep that follows Bradley's is a 1950-1952 Model M38 (wipers below windshield) which won't exist until five years after WWII ends.
Factual error: In the scene of the high level meeting during the initial stages of the Battle of the Bulge, Bedell Smith is conducting the meeting in General Eisenhower's behalf. In fact, General Eisenhower was present at the meeting.
Factual error: In the washroom scene where Gen. Montogomery is speaking with Gen. Smith; Monty breathes on the mirror in order to make a drawing of Sicily. The condensed "breath" remains far too long, the same happens when Smith makes his drawing on the mirror.
Factual error: At the end of Patton's speech in Knutsford, just when the marching band starts playing, you can see a modern (in 1970) tanker truck driving in the background for a couple of seconds.
Factual error: When he is talking with General Bradley at the Carthaginian ruins near the beginning of the film and he recites his re-incarnation poem. If you look very carefully at the sky you will see a jet streaking, from left to right on the screen. Easy to miss but I've replayed it many times. The object is going in a straight line and going way too fast to be an internal combustion engine plane.