Complex sentence: Although the Congress of Tucumán had already formalized the flag of Argentina, the Army of the Andes did not use it, choosing a banner with two columns, light blue and white, and a coat of arms roughly similar to the Coat of arms of Argentina.
Split into simpler sentences: Although the Congress of Tucumán had already formalized the flag of Argentina, the Army of the Andes did not use it. It used instead a banner with two columns, light blue and white, and a coat of arms roughly similar to the Coat of arms of Argentina.