The War of the Regrets. Immediately preceded by & coincident with - The Second Farce. Led directly to The War of the Piece.
The War of the Regrets (Guerra de Los Lamentos) was fought between 1901 and 1905 between Argentina and the alliance between the former republic of Uruguay and Brazil.
All began when 5 fishing vessels (all vessels named Regret I to Regret V, Lamento I to Lamento V in Spanish) were caught fishing in Argentinian waters without license and captured by AN. All the 5 crews were condemned to a 50 years prison conviction. Tensions raised then, and Uruguayan government in alliance with Brazil declared war to Argentina claiming protection of their maritime borders. War ended with Argentinian annexation of Uruguay and the Brazilian state of Rio Grande Do Sul.
The Second Farce is the OTL Chaco War (1900-1904) that was fought in 1932-1935. Its known as the Second Farce, being the First Farce, the OTL Paraguayan War. As OTL, the end of the Second Farce will set the final boundaries between Bolivia and Paraguay, but ITTL, in 1909 Paraguay became a regional oil exporter.
The War of the Piece was an armed conflict between 1911 and 1913 between Paraguay (backed by Argentina and Chile) and Brazil over the oil rights near Porto Murtinho, on the brazilian-paraguayan border. It was known for a picture taken in the middle of the tensions that became famous, having a brazilian soldier stealing a paraguayan oil well piece. Ended with a Friendship and Trade Treaty, with more benefits for Paraguay.
The Canadian-Suriname War