Who is the Italian that is mentioned in the first sentence of Homage to Catalonia?

The Italian in question is a militiaman that Orwell meets at the Lenin barracks in Barcelona. He first sees him standing over a map, a look of puzzled intensity on his face as he tries to make sense of it. However, Orwell takes an instant liking to the man; there is something about his face, a mixture of honesty and ferocity that appeals to him. When someone mentions that Orwell is a foreigner, the Italian comes across and shakes him warmly by the hand. That is the last time Orwell ever sees him.
The memory of the Italian stays in Orwell's mind because it sums up many of his experiences of fighting in the Spanish Civil War. In the figure of the Italian militiaman we see the shabbiness, the ferocity, the extraordinary bravery, and the sense of camaraderie among the common soldiers of the Republican forces.