A horizontal triband of blue, white, blue.
During the Argentine War of Independence (1810-1818) Manuel Belgrano, a committee member of the Primera Junta (First Assembly; the first independent government of Argentina) and military captain realized that the patriots fighting for independence from the royalist Spanish forces were using the same colours (yellow and red). Belgrano went about creating a cockade (a rosette made of ribbon) or blue and white to differentiate friendly troops.
On 18 February, 1812 the government decided to use a national cockade of blue, white and blue. Belgrano used the same colours to design a horizontal bicolour of white over blue flag which his troops would take an oath to on 27 February, 1812. The government rejected the flag. The flag would continue to be used for the military. Belgrano would go on to design the horizontal tribands; one blue-white-blue, another reversed white-blue-white.
To prevent the flags falling into enemy hands the flags were given to a priest at the chapel in the hamlet of Titiri new the village of Macha, Bolivia. The flags were hidden behinda portrait of Saint Teresa of Avila. Belgrano was summoned back to Buenos Aires and the flags would be forgotten about.
In 1885, the new priest in in the chapel discovered the flags during a restoration of the building. The flags were moved to the Museum of Independence in Sucre, Bolivia. The museum kept the white-blue-white flag and the other was returned to Argentina in 1896.