Answer by taking a quote from the following article:

Laurence Kerr Olivier, Baron Olivier,  (; 22 May 1907 - 11 July 1989) was an English actor and director who, along with his contemporaries Ralph Richardson and John Gielgud, dominated the British stage of the mid-20th century. He also worked in films throughout his career, playing more than fifty cinema roles. Late in his career, he had considerable success in television roles.

Olivier had intended to step down from the directorship of the National Theatre at the end of his first five-year contract, having, he hoped, led the company into its new building. By 1968 because of bureaucratic delays construction work had not even begun, and he agreed to serve for a second five-year term. His next major role, and his last appearance in a Shakespeare play, was as Shylock in The Merchant of Venice, his first appearance in the work. He had intended Guinness or Scofield to play Shylock, but stepped in when neither was available. The production by Jonathan Miller, and Olivier's performance, attracted a wide range of responses. Two different critics reviewed it for The Guardian: one wrote "this is not a role which stretches him, or for which he will be particularly remembered"; the other commented that the performance "ranks as one of his greatest achievements, involving his whole range".  In 1969 Olivier appeared in two war films, portraying military leaders. He played Field Marshal French in the First World War film Oh! What a Lovely War, for which he won another BAFTA award, followed by Air Chief Marshal Hugh Dowding in Battle of Britain. In June 1970 he became the first actor to be created a peer for services to the theatre. Although he initially declined the honour, Harold Wilson, the incumbent prime minister, wrote to him, then invited him and Plowright to dinner, and persuaded him to accept.  After this Olivier played three more stage roles: James Tyrone in Eugene O'Neill's Long Day's Journey into Night (1971-72), Antonio in Eduardo de Filippo's Saturday, Sunday, Monday and John Tagg in Trevor Griffiths's The Party (both 1973-74). Among the roles he hoped to play, but could not because of ill-health, was Nathan Detroit in the musical Guys and Dolls. In 1972 he took leave of absence from the National to star opposite Michael Caine in Joseph L. Mankiewicz's film of Anthony Shaffer's Sleuth, which The Illustrated London News considered to be "Olivier at his twinkling, eye-rolling best"; both he and Caine were nominated for the Academy Award for Best Actor, losing to Marlon Brando in The Godfather.  The last two stage plays Olivier directed were Jean Giradoux's Amphitryon (1971) and Priestley's Eden End (1974). By the time of Eden End, he was no longer director of the National Theatre; Peter Hall took over on 1 November 1973. The succession was tactlessly handled by the board, and Olivier felt that he had been eased out--although he had declared his intention to go--and that he had not been properly consulted about the choice of successor. The largest of the three theatres within the National's new building was named in his honour, but his only appearance on the stage of the Olivier Theatre was at its official opening by the Queen in October 1976, when he made a speech of welcome, which Hall privately described as the most successful part of the evening.

who were the military leaders he played?
Field Marshal French in the First World War film Oh! What a Lovely War, for which he won another BAFTA award, followed by Air Chief Marshal Hugh Dowding