Peruvian Police. The first time this stadium hosted the derby was on 26 June 2002—the first leg of the Apertura play-off—where Universitario won 1–0. Alianza's fans, in the southern stand, reacted violently to the loss by vandalizing the premises and causing two reported stabbings. Consequently, La U was forced to play all future derbies at Estadio Nacional where the Instituto Peruano del Deporte installed artificial turf which is constantly criticized by the First Division players. For the next five years this derby was not played at this stadium. On 14 September 2008, the derby returned to the Estadio Monumental with a loss for Universitario. This stadium was rejected as a venue for the Copa América 2004 because of problems with Alfredo Gonzalez, President of Universitario de Deportes, and the stadium's owners. Many saw this as a typical bullying behavior on the part of the president since this stadium would have been the perfect venue to host the 2004 Copa América intro as well as final games. Supporters Universitario's supporters are one of the largest in Peru, only rivaled by Alianza Lima's supporters. Universitario's ultra groups are known as Barra Oriente and Trinchera Norte. Asociación Barra Dale U, the official name of the Barra Oriente, started in 1968 that notably grew over the years. Trinchera Norte is a barra brava that was formed in 1988; in contrast to Alianza Lima's supporters, named "Comando Svr", "Sicarios", and others. The two most popular teams in Peru are Universitario and Alianza Lima. They are at the top of the polls conducted by many different groups. The group Apoyo, Opinion y Mercado in 2006 revealed that Alianza Lima was popular amongst 35%, followed by Universitario, with 32%. In 2005, a study by Grupo de Opinión Pública de la Universidad de Lima showed that Universitario was the most popular team in Lima and Callao with 31.7% followed by Alianza Lima with 29.3%. However, in 2006 and 2007 Alianza Lima appeared first in their polls. There was a narrow margin in 2007 as Alianza Lima reached 29.6% and Universitario followed with 29.5% under a margin of error of ±4.16% In 2009, the university's results varied because Alianza reached first with 40% and Universitario second with 35.5% under a margin of error of ±4.47%. Another group known as CPI, revealed in May 2008 that Universitario was favored by 32% whilst Alianza Lima was favored by 33.5% under a