The Monumento a los Defensores de Churubusco is on the south grounds of the National Museum of the Interventions. The former monastery was the center of one of the most important battles of the US invasion of Mexico. The battle raged for several days in August of 1847. Surprisingly, this monument dates from way back in 1856 as a tribute to the many who lost their lives in defense of Mexico City.
The battle saw some 1,400 Mexican forces pitted against 8,500 on the side of the US forces. It marked the defeat of the celebrated Batallón de San Patricio. This force of Irish and European forces, mostly deserters from the US army, remains important to the memory of the battle and the entire war. Some 50 combatants from the Batallion were hanged for desertion during court martials organized in the aftermath of the battle. They’re also eulogized in the street name where today stands the Churubusco Market south of the monument and across the San Mateo Churubusco neighborhood.
Further details on the battle are available in the entries on the museum itself, and in the somewhat better-known monument to General Anaya, on the western museum grounds. There’s more information on the ancient history of the site of the monastery in the article on San Diego Churubusco, one of the original settlements of Coyoacán.