This article explains why homicides related to drug-trafficking operations in Mexico have recently increased by exploring the mechanisms through which this type of violence tends to escalate. It is shown that drug-related violence can be understood as the result of two factors: (a) homicides caused by traffickers battling to take control of a competitive market, and (b) casualties and arrests generated by law enforcement operations against traffickers. Both sources of violence interact causing Mexico to be locked into a “self-reinforcing violent equilibrium” in which incremental increases in traffickers’ confrontations raise the incentives of the government to prosecute traffickers which promote further confrontations with traffickers when, as a result of the detention of drug lords, the remnants of the criminal organization fight each other in successive battles. This article presents quantitative evidence and case studies to assess the importance of the two mechanisms. It uses a unique dataset of recorded communications between drug traffickers and statistics on drug-related homicides.