During the First World War he enlisted in the Royal Italian Army as a volunteer, reaching the rank of captain by 1918; after the end of the war he was among Gabriele D’Annunzio’s legionnaires who occupied Fiume in 1920, and in the same year he joined the National Fascist Party.

Before the coup, Chierici had warned Mussolini that the members of the Grand Council of Fascism were preparing to vote a motion of no confidence against him, but after Mussolini's arrest he ordered his men to participate in the repression of unrest caused by Fascist loyalists in Rome.

[5] Chierici was then reinstated by the new prime minister Pietro Badoglio to the rank of lieutenant colonel of the Royal Italian Army, and given command of an Alpini battalion in South Tyrol.

[1][2] After the Armistice of Cassibile Chierici was arrested in Rome by the Nazis and handed him over to the authorities of the Italian Social Republic.

Considered a traitor, he was repeatedly tortured and died in prison in unclear circumstances; according to most sources he was murdered in his cell, possibly in order to prevent him from testifying at the Verona Trial about the events of 25 July 1943.