Riot police swept thousands of striking teachers out of the heart of Mexico City on Friday, driving protesters through the streets with tear gas and water cannons in a swift end to the weeks-long occupation of the Zocalo plaza over reforms to the dysfunctional national education system.
It was a dramatic reassertion of state authority after weeks of near-constant disruption in the centre of one of the world's largest cities. The teachers have marched through the capital at least 15 times over the last two months, protesting over President Enrique Pena Nieto's plan to break union control of education with a new system of standardised teacher testing that becomes law on Tuesday.
Authorities did not immediately report any injuries. Federal police chief Manuel Mondragon said more than 20 demonstrators were arrested.
The teachers' demonstrations have slowed passage of Mr Pena Nieto's education reform and the pace of his wider agenda of structural reforms, which seeks to restructure some of Mexico's worst-run institutions, including the weak tax-collection system and underperforming state oil company.
Mr Pena Nieto will almost certainly gain significant political capital if the Friday afternoon operation, led by federal instead of city police, definitively ends the demonstrations that have snarled traffic for weeks in Mexico City.
There was additional pressure to clear the Zocalo where the teachers had been camping out before the president's first traditional Independence Day celebration in the massive colonial-era square on Sunday and Monday.
The confrontation erupted after the teachers armed themselves with metal pipes and wooden and blocked off the Zocalo with steel grates and plastic traffic dividers, threatening to scuttle the Independence Day gathering.
The government responded that celebrations, including the president's shout of independence from a balcony of the National Palace overlooking the Zocalo, would take place in the square as scheduled on Sunday night.
The teachers, many veterans of similar battles with police in poor southern states, said they would not move from the square where they have camped out since last month. Some fixed knives and nails to wooden planks and declared themselves ready to fight. Others set up sewage-filled portable toilets in the path of police vehicles.
Shortly after 4pm, the police swarmed in, shooting tear gas canisters and spraying water from armored trucks. Protesters hurled sticks and chunks of pavement broken from the streets around world-famous tourist attractions including the Metropolitan Cathedral, the Templo Mayor and the National Palace. But within a half hour, police had cleared the Zocalo and much of the surrounding historic center of virtually all demonstrators. Union organisers said they would reassemble away from the main plaza at the nearby Monument to the Revolution. Small knots of teachers, self-described local anarchists and other supporters hurled bottles and rocks at police on some of the main avenues of downtown Mexico City.