Here is his introduction to The Ten Commandments:
So he was a celebrity and he also appeared as himself in Sunset Boulevard (Billy Wilder 1950), with Gloria Swanson who was his leading lady in the silent era.
That year, 1950, was an interesting one for DeMille and for Hollywood in general because of the intense political intrigue being played out at SDG, the Screen Directors Guild (which later became DGA, the Directors Guild of America), where most directors were members. That is the subject of today's Easter post.
The late 1940s and 1950s were filled with fears and paranoia about Communists, the Red Scare, which infected all parts of the United States. The most famous examples are from Congress where in the House of Representatives there was HUAC (House Un-American Activities Committee) and in the Senate there was Joseph McCarthy, the junior senator from Wisconsin. DeMille was an anti-Communist crusader, a friend of McCarthy, and an influential member of the board of the SDG. He had been working during the 1940s to fill the board with like-minded people, like Albert S. Rogell, George Marshall and Sam Wood, as the board held the real power in the Guild. After Congress, against the veto of president Truman, had enforced that all federal employees signed a loyalty oath (in effect declaring that the signed was not a Communist) DeMille wanted every member of the SDG to sign one too. This is when he and fellow filmmaker Joseph L. Mankiewicz became enemies.
Mankiewicz was at the time at the height of his powers, fresh from the remarkable success of A Letter to Three Wives (1949), possibly his best film. In 1950 he made two other distinguished films, No Way Out and All About Eve, the latter for which he would win Oscars for best writing and best directing, just as he had for A Letter to Three Wives. His films were the opposite of DeMille's, sophisticated and intelligent dramas and comedies. But DeMille had recommended that he take over the position as president of the SDG, after George Stevens, and this is what happened. DeMille probably thought that Mankiewicz would be malleable to his wants, but this turned out to not be the case.
The conflict was not so much about an oath per se, most members of SDG, including Mankiewicz, were in favour of signing such a thing. In August of 1950, when Mankiewicz was on a ship sailing from France to the US, DeMille and his board had sent out a ballot to all the members of SDG where they could vote yes or no to such an oath. 547 voted yes, 14 voted no, and 57 did not vote at all. (Whether those who voted yes all did so because they really believed in it or because they were afraid of ending up on a blacklist is a valid question.) But DeMille and his faction argued that the oath should be mandatory, for all members, and official, so that anybody could see who had signed. The result would be that whomever refused to sign would more or less end up on a blacklist. The board had already voted against this, but DeMille and his faction were not satisfied with that no-vote. So this is the situation that faced Mankiewicz when he came back from his trip, on August 23. When DeMille understood that Mankiewicz would not budge in his resistance to a mandatory oath, he and his closest associates tried to get Mankiewicz kicked out. On October 11, DeMille called a secret board meeting and only invited those he knew agreed with him (which meant that for example George Stevens got his invite to the meeting after it had already begun) and they decided to send out a new ballot to members of the SDG for a recall of Mankiewicz, with no motivation and without official SDG approval. The ballot was then sent out by motorcycle dispatches during the late evening and night of October 12, to most members of the SDG, with the exception of 55 members considered too loyal to Mankiewicz.
Obviously, Mankiewicz and his friends were to be kept in the dark but apparently Mankiewicz's brother, Herman, got word of it and called him up saying he was being impeached. Mankiewicz quickly set up a secret meeting of his own to counter DeMille's attack, on the evening of October 13. He had a lawyer, Martin Gang, take out an injunction against DeMille's ballot and got hold of 25 supporters among the SDG members who could sign on to a request for a general meeting for the SDG. (25 signatures were needed for that.) In the nick of time he managed to secure them and a meeting was called. It was held on the evening of October 22, beginning at 8:00 pm, and chaired by Mankiewicz. There were three things on his agenda: to clear his name and save his presidency, to dismiss the idea of a general, mandatory and public oath, and to restrain the power of the board (and DeMille) and give it back to the members.
So far, most things had gone DeMille's way but he was so arrogant and offensive at the meeting that he managed to turn almost everybody against him, including some of his ideological partners. It is usually said that it was John Ford who decisively turn things around so that Mankiewicz prevailed, and DeMille lost, but when Ford intervened the game was pretty much already over. First the members were appalled when DeMille seemed to suggest that Mankiewicz's 25 supporters were in one way or another closeted Communists. Among those who ventured their anger were John Cromwell, George Seaton, William Wellman, Delmer Daves, John Huston and William Wyler. Then they became even angrier when told of DeMille's deceitful attempt to force out Mankiewicz, revealed by George Stevens who had spent the week conducting a thorough investigation into DeMille's shenanigans and now presented his result. (Stevens also announced his resignation from the board out of sheer disgust.) And, finally, Ford intervened and suggested that the whole board (of which he too was a member) resigned, including DeMille. That is how the meeting ended, after over six hours of heated discussions. The board resigned and it was decided to put together a committee of five members to investigate the whole affair. DeMille picked up his papers and walked away, a defeated man.
That was an effort to do a fair summary but over the years there have been conflicting stories about it, and who did or said want to whom has often been misleading. Mankiewicz's real position regarding the oath has also been confusing, even his own telling of the story, and the oath remained in one form or another until the Supreme Court struck it down in 1966.
As an example of the confusion, here is first a quote from Scott Eyman's book The Life and Times of John Ford (1999):
It was around this point that DeMille read out the names of the  men who had signed the petition to call the meeting, emphasizing, in many cases, their foreign origins - "Villiam Vyler," etc. Although this moment is not preserved in the transcripts, everybody still alive who was there says that DeMille did in fact do it, alienating all those in the middle of the argument.Eyman then quotes Richard Fleischer as saying (in an interview) "When DeMille took over on the stage, he read the names of the people that had signed the petition to hold the meeting. Myself, Bob Wise, Mark Robson, among others. He read the names, and emphasized their foreignness, the Jewishness of the names, ridiculing them. And then he implied that they were all Communists. It was an outrageous thing to say." Eyman also quotes, apparently from the transcript, other directors' reactions, such as Delmer Daves "I resent beyond belief the things that you said as you summarized the 25 men. ... I think it was disgraceful." (p. 381-382)
But here is Scott Eyman again, some years later, in his book Empire of Dreams: The Epic Life of Cecil B. DeMille (2010):
It was around this time that many who were present would, in later years, claim that DeMille read out the names of the men who had signed the petition to call the meeting, emphasizing, in many cases, their foreign origins - "Villiam Vyler," "Joseph Mankievitch," etc. The implication of a Jewish cabal behind Mankiewicz has been Exhibit A in the case against DeMille as an anti-Semite. But the transcript of the meeting contains no such occurrence, nor does anybody else in the meeting refer to such a moment. In fact, at one point DeMille explicitly states that he has named no names, named only the dubious (in his mind) associations of some of the petitioners, which is confirmed by a statement Vincent Sherman made later in the meeting. In all the extensive literature devoted to the meeting, nobody ever claimed DeMille had done such thing until 1984, when Fred Zinnemann published his memoirs - and Fred Zinnemann was not at the meeting. It's only after 1984 that Mankiewicz and other men who were there take up the story. (p. 406)Eyman suggests that DeMille's arguments at the meeting "was converted by time and the trick of memory into an actual speech that strongly implied anti-Semitism." (p. 407) Eyman is probably overstating his case, and he does not mention his own participation in this. It is also worth noting that Eyman is wrong, because Fred Zinnemann did not publish any memoirs in 1984. They were published in 1992, Fred Zinnemann: An Autobiography, and make not such reference to DeMille. Zinnemann only says that DeMille was the lead member of the board. (p. 97)
The rumours about that alleged anti-Semitism, and the counter-arguments against it, have taken a life of their own. When for example was this first reported? It was not in Zinnemann's autobiography, so much is certain. Another charge has been that it was Billy Wilder who first made the accusation, referenced in Ed Sikov's book On Sunset Boulevard: The Life and Times of Billy Wilder (1998). But there Wilder is quoted as saying, in 1972, that DeMille mocked him, and others, for being foreigners (p. 332), not explicitly for being Jewish (although the two were often linked). In Hollywood Divided (2016), Kevin Brianton suggests that it was Mankiewicz who started the rumour, but much later, in the 1980s. So possibly DeMille never did say those things. But he does not exactly come out well from this affair anyway, even without the possible anti-Semitism.
This whole thing has become something of a mythical event and filmmakers are still judged according to how they behaved during this affair, even though it is often difficult to comprehend what exactly happened and why. But that it was an important event is obvious. A defining moment in the history of Hollywood, although what it defines is foggy.
Somebody who is never mentioned, even though he is one of the most important directors, is Alfred Hitchcock. I do not know whether he was unable to attend, he was shooting Strangers on a Train (1951) around New York and Washington at that time, far from Los Angeles, or if he did not want to be involved. According to Patrick McGilligan, in Alfred Hitchcock: A Life in Darkness and Light (2003), Hitch did not like DeMille, he "offended Hitchcock's mild brand of socialism." (p. 257)
The film Mankiewicz made after this affair, People Will Talk (1951), was clearly influenced by his experience. Its hero, played by Cary Grant, is being investigated and threatened by a bitter colleague played by Hume Cronyn. But that is only one of the many themes and plot points in this remarkable film. DeMille's next film was The Greatest Show on Earth (1952), which is clearly a labour of love and which won two Oscars, including Best Picture, but I find it unbearably tedious.
My primary sources:
Pictures Will Talk: The Life and Films of Joseph L. Mankiewicz (1978) by Kenneth L. Geist.
Fred Zinnemann: An Autobiography (1992) by Fred Zinnemann (and Alexander Walker).
On Sunset Boulevard: The Life and Times of Billy Wilder (1998) by Ed Sikov.
The Life and Times of John Ford (1999) by Scott Eyman.
Alfred Hitchcock: A Life in Darkness and Light (2003) by Patrick McGilligan.
Empire of Dreams: The Epic Life of Cecil B. DeMille (2010) by Scott Eyman.
Hollywood Divided: The 1950 Screen Directors Guild Meeting and the Impact of the Blacklist (2016) by Kevin Brianton.