In Montevideo he got a degree as lawyer: he had already finished his studies in Buenos Aires, but refused to make the oath under Rosas' government. Alberdi thought that the real problem in Argentina was not specifically Rosas, but the society that supported him. As a result, he thought that the generation of '37 should understand the reasons of such popular support, and how to earn it for themselves. He worked in antirosist publications, such as "El Grito Arjentino" () and "Muera Rosas" (). He also wrote theater plays, "La Revolución de Mayo" () and "El gigante Amapolas" (). The name of this last one was a word play with the last name of Rosas, as "Rosas" can be also understood in the Spanish language as the plural form of "Rosa", the Rose flower. Alberdi worked as well as secretary of Juan Lavalle, who made a military campaign against Rosas during the French blockade of the Río de la Plata, but left him for political disagreements. Manuel Oribe, president of Uruguay deposed during the Uruguayan Civil War and allied to Rosas, laid siege to Montevideo in 1840, so Alberdi left the city and moved to Europe, alongside Juan María Gutiérrez.