Corporal Diaz (French: Caporal Diaz) was an army official in San Theodoros. He is first seen being demoted from the rank of Colonel by General Alcazar who replaced him with Tintin after Diaz complained that San Theodoros had too many colonels and too few corporals.
Diaz was a colonel and Alcazar's aide-de-camp. But he was demoted after complaining about the amount of colonels and lack of corporals and suggested that Tintin become a corporal. But he instead became a corporal after saying this. Because of that, Diaz swore a vendetta. He joined a terrorist group.
In revenge, he engaged in repeated, unsuccessful assassination attempts against Alcazar.
He first threw a bomb in Alcazar's office. But Tintin saw it and threw it out, knocking Diaz into a fountain.
Then, he brought a bomb, but forgot to bring matches. Coincidentally, Alcazar threw a cigar out the window and landed on Diaz's hat, catching him on fire and forcing him to jump into a fountain.
Then he finally lights the bomb and hides behind a statue. The bomb blows up, but the head of the statue he was hiding behind was blown off and fell on Diaz's head, and Alcazar only suffered from Jaundice, a type of shock. He rebuked by his boss for incorrectly planting the bomb.
His last attempt, which lead to his death, was when he was given a time bomb that explodes at exactly 11 o'clock. Along the way, Diaz notices his watch stops working and looks at a clock. But all the city clocks were also incorrect. Repairmen were hired to fix them, and when Diaz looked at one again, an hour later, the actual time was 11 o'clock, 1 hour later than what Diaz thought. Ironically, meanwhile, Alcazar had arrested and sentenced Tintin to death due to faked evidence against him and promoted Diaz back to colonel just before the bomb blew up, killing Diaz.