The hold-up was caused by activists trying to block the shipment of nuclear waste from southern to northern Germany by digging holes under the track and cementing their arms inside with quick-drying cement. "We shall not be moved," sang thousands of other protesters occupying the road linking the end of the railway line to the nuclear storage site of Gorleben, 12 miles to the east. For nearly a week, environmentalists had played cat and mouse with police, erecting dummy barricades at one place before vanishing into the forests, only to appear at another crossroads.
The train's meandering course from southern Germany to the moorlands along the Elbe had been shadowed by trouble. Protesters clashed with police at several points along the route, throwing stones, sabotaging railway lines and charging at the troops in battle formations.
The authorities were taking no chances. In a 40-mile radius around Dannenberg, the state was out in force. Police buses lurked in lanes, helicopters hovered overhead and motorists were confronted with an unexpected traffic hazard: convoys of armoured personnel carriers (APCs) forcing their way in from side-roads, evidently oblivious to give-way signs.
The railway station at Dannenberg was ringed by police and border guards - some of the 30,000 hired as nuclear guards for the week. The resolve of the police had to be stiffened by the dispatch of thousands of fellow officers from the east, perhaps considered to be better versed than their western colleagues in the art of wielding a truncheon.
The toughest units were charged with defending the railway station from hard-core militants. The two sides faced off across the tracks. The police in riot gear shouted from behind a line of APCs while the anti-nuclear activists hid among their battered cars.
The law enforcers had slept in hotels, schools and gyms requisitioned by the authorities. The protesters had spent the previous nights in tents.
But the battle was not entirely uneven, even if the activists were outnumbered three to one.
Local farmers joined the protest by blocking roads with their tractors, and the regional fire brigades refused to supply the water cannons with their ammunition.
The protesters knew the terrain better than their "foreign" opponents, and many had taken the precaution of bringing crash helmets to the encounter.
The conflict, they hope, will strangle the nuclear industry by closing the last outlet for its end-product, which will remain lethal for centuries.
Apart from the escalating price of guarding the annual train journey, the social cost of nuclear power is also beginning to appear too high.
The issue has divided Germans along regional lines, pitting the prosperous south against the poorer north.
The battle of Gorleben is also turning into a left-versus-right conflict, with a measurable electoral fall-out. "This shipment must be the last," said Gerhard Glogowski, the Social Democrat interior minister of Lower Saxony, the Land now notorious for a blot on its map called Gorleben.