Over the weekend, a wave of protests in Chile set off by an increase in subway fares deteriorated into widespread looting, vandalism and arson.

President Sebastián Piñera declared a state of emergency, imposed curfews and ordered the armed forces to restore order — measures that were jarring for Chileans who lived through a repressive period of military rule in the 1970s and 1980s.

The scenes of mob violence were striking in a country that has long been regarded as an exemplar of economic and political stability in a turbulent region.

Here is what you need to know to understand what led to this crisis.

How did this start?

A modest subway fare increase that started on Oct. 6 led high school students to jump turnstiles at metro stations in Santiago, the capital, earlier this month. They promoted it as an act of civil disobedience using the hashtag #EvasionMasiva, or “Mass Evasion,” on social media.