LTC Darby refers to West Point as "the point" while interviewing a new lieutenant from West Point. West Pointers do not EVER refer to West Point as "the point." Darby was class of '33.
The German troops seen in the early fighting in Sicily and Italy are wearing the 1916 'Stahlhelm' helmet, clearly identified by its size and large lugs protruding from the sides. This WWI helmet had actually been fully replaced in 1935 by the more streamlined version used by all German troops in WWII.
When Lt. Colonel Darby is seen wearing an overseas cap, the cap is missing Darby's rank insignia (a silver oak leaf).
Darby was in Northern Ireland when assigned to the 1st Ranger Battalion, not at the Pentagon.
The Rangers are seen wearing the red and black RANGER scroll patch that was unofficial until 1984. The authorized shoulder patch during World War II was a blue and yellow diamond with RANGER embroidered inside.
The German tanks shown in scenes at the Battle of Cisterna are M-41 walker bulldog tanks, which were made first made in 1951.
The women's hairstyles and clothing do not match the period. The women appear to have hairstyles of the 50s, not the 40s.
The Battalion is fired on from a hidden machine gun. One man is shot dead muttering "well I'll be damned," as he dies. The rest of the battalion gets up and leaves without ever dealing with the machine gun.
At the end of the film Darby is seen departing Anzio in his Ranger insignia for return to the US. In actuality, Darby served two more months after the Rangers were disbanded as commander of the 179th Infantry Regiment, an Oklahoma National Guard unit. Pictures at the time show him wearing the standard insignia of the 45th Division before his return to Washington.
The lieutenant is invited to dinner by an Italian girl in a liberated Italian town who speaks with with French accent.