What happened next made the Tiananmen Square re-run look almost tame. As in Peking two decades later, however, tracks were swiftly erased by Mexican authorities anxious to transmit an image of tranquillity 10 days before the opening of the first Olympic Games granted to a Third World nation. To this day, most Mexicans, and most of the world, remain largely in the dark over the extent of the Tlatelolco massacre.
Independent accounts suggest around 300 people, including women and children passers-by, were slaughtered by the Mexican army, police and special 'Olympic Battalion' created for the Games. More than 1,000 were arrested and hundreds never seen again. No one knows whether the government, army or police planned the massacre or it was a botched attempt to capture striking student leaders.
There were helicopters overhead, one of which suddenly dropped green flares, according to eyewitnesses. In what must have been a dramatic re-enactment of what Cortes faced on the same spot, with only the garb and weapons changed, hundreds of soldiers emerged from the Aztec ruins and opened fire with automatic rifles. Cortes at least had the firepower to respond.
The daily El Universal reported that many victims, including women and children, died of bayonet wounds as troops, with orders to detain student leaders, killed anyone trying to flee.
The shooting went on for more than an hour as students, civilians and journalists lay crouched or sought shelter. Local and foreign journalists, including Italy's Oriana Fallaci, were herded out, and the square sealed off, before they could assess casualties. By the time journalists were allowed back the following day, the square was deserted. According to nearby residents, army lorries removed bodies during the night while firemen were called in to wash away bloodstains.
The authorities admitted only 32 dead but as rumours of a greater massacre spread, a spokesman for the president, Gustavo Diaz Ordaz, assured the nation and the world that the Games would go ahead in complete security. 'The focus of agitation has been eliminated,' he declared. One of the few officials to speak out was writer Octavio Paz, then Mexico's ambassador to India, who quit his job in protest. Another Mexican writer, Elena Poniatowska, in her book, The Night of Tlatelolco, described the massacre as 'a scar that has never healed'.
Ten days after the massacre, the world saw the Olympic flame lit and white doves released from the Olympic stadium but Mexico's state-controlled television ensured thousands of troops and police were kept off camera.
The authorities could not, however, blot out the effects on the nation's consciousness. The date is seen by many as the start of what is essentially another, painfully slow, Mexican revolution. Many believe the massacre spelled the beginning of what will sooner or later be the end of Mexico's all-done-by-mirrors 'democracy' - in fact, firm control by the Institutional Revolutionary Party (PRI).
A so-called 'Commission on Truth', an independent group of 20 intellectuals, is working on a definitive account of the massacre in an effort to exorcise the damage to the national pysche.
Today, as every year since, Mexicans will march to the Square of the Three Cultures, so named to mark the Indian, colonial and modern epochs, all of which are represented in the surrounding architecture. This year, after education authorities for the first time allowed references to the massacre in textbooks, hundreds of thousands may show up. Others, still intimidated by the PRI's omnipotence, will stay away.