The original screenplay for The Undefeated was written by Stanley L. Hough and Casey Robinson, based on Hough’s story, as noted in the 15 Dec 1967 DV, which announced Twentieth Century-Fox Film Corp.’s acquisition of the property. The studio brought in James Lee Barrett to write the final script, and director Andrew V. McLaglen’s involvement was reported in a 21 Aug 1968 DV item. The Undefeated was set to be McLaglen’s first picture in a recently signed three-year deal with Fox. John Wayne’s casting was announced shortly after McLaglen’s hiring, in the 23 Aug 1968 DV.
       According to a 16 Oct 1968 Var brief, filming was originally scheduled to take place in Texas in fall 1968; however, the shoot was delayed to allow John Wayne to finish his role in True Grit (1969, see entry). Subsequent plans were made to film in Durango, Mexico, instead of Texas, and production got underway on 7 Feb 1969, as stated in the 14 Feb 1969 DV.
       A few days prior to the start of filming, Wayne fell in a restaurant in Guaymas, Mexico, and broke two ribs, as reported in a 5 Feb 1969 DV news item. To recuperate, the actor went home, and he was due to return to set on 17 Feb 1969. In the meantime, McLaglen planned to shoot scenes involving Rock Hudson. The 13 Feb 1969 DV claimed that Wayne’s fall had taken place during an interview with a newspaperman, when Wayne had tried to move to a quieter part of the restaurant and had slipped on the tile floor. As noted in a 13 Apr 1969 LAT interview with Wayne, the incident prompted rumors that he had been in the midst of a drunken tirade after arriving in Guaymas by private plane and not receiving “a royal reception.” Wayne ultimately admitted that he had been drinking before the fall. After returning to work, the actor injured himself a second time, on set in Baton Rouge, LA. The 21 Apr 1969 DV noted that, during a scene in which he was on horseback, Wayne’s saddle cinch had slipped, causing the actor to fall and dislocate his shoulder. Although he was rushed to the hospital, he reportedly returned to set that day and continued acting in a scene with Hudson.
       Principal photography was completed by early May 1969, according to a 7 May 1969 Var brief. The final cost of the film was cited as $7 million in the 5 Nov 1969 Var. The price of shooting in Durango had not been as low as initially expected, the 14 May 1969 Var noted, as local vendors had reportedly overcharged for food, housing, and other services. Angered by the price gouging, Wayne allegedly threatened never to shoot in the city again. However, a 26 Aug 1969 DV item noted that, after the governor of Durango had personally promised the overcharging would not be repeated, Wayne and McLaglen decided to return to Durango for the filming of Chisum (1970, see entry).
       A 4 Oct 1969 world premiere was scheduled to take place in New Orleans, LA, according to the 23 Jul 1969 Var. Advance publicity for the film included a cross-promotion with General Motors, as stated in the 24 Sep 1969 Var, which estimated the tie-in campaign would cost $3 million. The film opened the week of 19 Nov 1969 in Los Angeles, CA. Following tepid reviews, the 7 Jan 1970 Var reported a cumulative gross of $4.5 million in film rentals, to date.
       The following actors were listed as cast members in DV and Var items published between 2 Jan 1969 and 6 Mar 1969: Alberto Morin ; Fred Dick Bullock; Jerry Gatlin; John Hudkins; James Burk ; Trini Villa, son of Pancho Villa; and José Salas.
       Antonio Aguilar, credited as “Tony Aguilar,” was a well-known singer in Mexico at the time of filming. The 3 Apr 1969 DV reported that, due to his popularity with Latin American audiences, the actor would receive above-the-title billing on all Spanish-language prints of the film.