One of the fighters in Pablo's band of guerrillas. To be more precise, he is a foundational member of the band. Though he is a loyal man, Agustín is one who makes hasty decisions and has a harsh temperament. He doesn't believe Pablo even though the man has the intelligence needed to be a good guerrilla. Agustín's foul mouth makes him one of the most noticeable characters from the beginning. The bloodlust is upon him throughout the story. Even more, he has the strongest case of it after Pablo. In fact, when a fascist patrol comes by, Agustín decides to kill them although it is not the part of the given instructions. Also, he is one of the characters who make false promises throughout the story. Even though Agustín claims several times that he desires to kill Pablo, it never happens. Besides, he is not good at sentry duty as he strives hard to remember the password. Nevertheless, as far as the mission is concerned, Agustín is someone who can be entirely trusted as he is actually courageous in fights. Besides, his intelligence helps him to understand that the band will need Pablo to succeed. He is the one who has got a thing for Maria before Robert Jordan. However, Agustín respected the woman's vulnerability. Regardless of own feelings, Agustín does everything possible to help Maria and Robert Jordan after he assures that their feelings are mutual. In this case, Agustín demonstrates his nobility and dignity. Consequently, Robert Jordan approaches Agustín as a good friend and the brother he never had.