ON MAY 1st the state of Jalisco in western Mexico felt like a war zone. An army helicopter was shot down with a rocket-propelled grenade. Smoke billowed from at least 11 banks and five petrol stations. Cars, buses and trucks had been commandeered to create 50-odd roadblocks in Jalisco and three neighbouring states; many were set alight. Fifteen people, including six soldiers and a government official, died in the violence.

The May Day mayhem was one of the most dramatic acts of defiance by drug gangs since an offensive against them began in 2006. It served notice that a relatively new group, the Jalisco New Generation Cartel, is willing to confront federal forces. And it called into question the federal government’s strategy of dealing with gangs mainly by killing or jailing their leaders.

New Generation has its roots in two older outfits. One was a faction of the Milenio gang, a pioneer in methamphetamine trafficking, which fell apart after its leader, Óscar Nava Valencia, was captured in October 2009. The other was a branch of the Sinaloa gang, whose chief, Nacho Coronel, was killed by the army in July 2010. New Generation saw off some local competition in Jalisco. Then it consolidated its position in other states after the authorities captured or killed the leaders of the fearsome Zetas and Knights Templars.

New Generation has claimed a big role in trafficking methamphetamines to the United States and cocaine to Europe, and has entered lucrative sidelines such as gun-running, kidnapping and extortion. New Generation has clashed bloodily with other groups, notably the Zetas, and has recently turned its fire on the police and army. On April 7th, the group ambushed a convoy of police on a country road in Jalisco, killing 15 and wounding five. The crackdown by the army after that outrage triggered the violence of May 1st.

“The criminal group responsible for the events today will be dismantled” just like the others, vowed Mexico’s president, Enrique Peña Nieto, on Twitter. But New Generation’s rise suggests that the government’s approach, which gives priority to eliminating “high-value targets”, is only working in some parts of the country.

Critics contend that the strategy of going after kingpins shatters their organisations into smaller groups that can be equally destructive. They have less capacity to move large quantities of drugs and avoid taking on federal forces. But they exploit and control some communities with unbridled ferocity, and rely on the complicity of corrupt politicians and businesses. The group that conspired with local police in the disappearance in September of 43 students originated in the breakup of the once mighty Beltrán Leyva gang.

The emergence of New Generation teaches a different lesson: it shows that new giants can be formed from the remnants of defeated groups. It may have miscalculated on May 1st, since it is now the federal authorities’ number-one target. Analysts say they will eventually catch up with its leader, Nemesio Oseguera Cervantes, alias El Mencho. But as Mexicans in Jalisco are beginning to learn, it is not enough to eliminate the kingpins and break up their organisations. Their successors can be just as lethal.