On December 14, 1818, the French privateer Hipólito Bouchard, sailing under the flag of the "United Provinces of Rio de la Plata" (Argentina), brought his ships La Argentina and Santa Rosa to within sight of the Mission; aware that Bouchard (today known as "California's only pirate") had recently conducted raids on the settlements at Monterey and Santa Barbara, Comandante Ruíz had sent forth a party of thirty men (under the leadership of a young Spanish lieutenant named Santiago Argüello) to protect the Mission at first news of the approach on the 13th.
Two members of Bouchard's contingent made contact with the garrison soldiers and made their demand for provisions, which was rebuffed with added threats: Lieutenant Argüello replied that if the ships did not sail away the garrison would gladly provide "an immediate supply of shot and shell".
In response, "Pirata Buchar" (as he was referred to by the Californios) ordered an assault on the Mission, sending some 140 men and two or three violentos (light howitzer cannon) to take the needed supplies by force.
The Mission guards engaged the attackers but were overwhelmed; the marauders looted the Mission warehouses and left minor damage to several Mission buildings in their wake, and reportedly set fire to a few of the outlying straw houses.
Reinforcements from Santa Barbara and Los Angeles, led by Comandante Guerra from El Presidio Real de Santa Bárbara, arrived the next day to no avail as the ships had already set sail.

Though the mission was spared, all ammunition, supplies and valuables in the area were taken.
Regarded today as one of the more colorful events in the Mission's history, an annual celebration is held to memorialize "The Day that Pirates Sacked the Mission."
On December 14, 1818, the French privateer Hipólito Bouchard, sailing under the flag of the "United Provinces of Rio de la Plata" (Argentina), brought his ships La Argentina and Santa Rosa to within sight of the Mission; aware that Bouchard (today known as "California's only pirate") had recently conducted raids on the settlements at Monterey and Santa Barbara, Comandante Ruíz had sent forth a party of thirty men (under the leadership of a young Spanish lieutenant named Santiago Argüello) to protect the Mission at first news of the approach on the 13th. Two members of Bouchard's contingent made contact with the garrison soldiers and made their demand for provisions, which was rebuffed with added threats: Lieutenant Argüello replied that if the ships did not sail away the garrison would gladly provide "an immediate supply of shot and shell". In response, "Pirata Buchar" (as he was referred to by the Californios) ordered an assault on the Mission, sending some 140 men and two or three violentos (light howitzer cannon) to take the needed supplies by force. The Mission guards engaged the attackers but were overwhelmed; the marauders looted the Mission warehouses and left minor damage to several Mission buildings in their wake, and reportedly set fire to a few of the outlying straw houses. Reinforcements from Santa Barbara and Los Angeles, led by Comandante Guerra from El Presidio Real de Santa Bárbara, arrived the next day to no avail as the ships had already set sail. 
Though the mission was spared, all ammunition, supplies and valuables in the area were taken. Regarded today as one of the more colorful events in the Mission's history, an annual celebration is held to memorialize "The Day that Pirates Sacked the Mission."
Mission San Juan Capistrano