Just after midnight, soldiers began running down stairs and storming the tunnels of a Berlin underground metro station.
Screams were heard coming from the yellow train carriages stopped mid-track, as shots were fired and gunpowder smoke filled the platform.
Overnight, the Jungfernheide U-Bahn station in Berlin's west was taken over by troops from Germany's Wachbataillon (Guard Battalion).
Better known for their ceremonial duties, the unit has been carrying out a series of urban warfare drills throughout the capital.
The soldiers are expanding their infantry capabilities to protect federal government infrastructure in a crisis.
As concerns grow that Russia could regain military capability to strike NATO territory as early as 2028, the battalion is preparing for "the worst-case scenario".
"Like the entire armed forces, we have the mission to become combat-ready," guard battalion commander, Lieutenant Colonel Maik Teichgraeber, told local media.
The Bundeswehr — the German Armed Forces — said a city such as Berlin posed many combat challenges including narrow streets, tall buildings, poor visibility and radio communication disruptions.
So it was important for soldiers to train under realistic metropolis conditions.
Lieutenant Colonel Teichgraeber said the U-Bahn station was a "very realistic" scenario as public transport was a common place for hostile forces and saboteurs to cause disruptions.
About 30 soldiers reportedly took part in the metro drill, alongside a group of actors playing wounded civilians and additional support teams.
The exercise, which went until about 4am, involved soldiers responding to an attack by fictional separatists.
The troops trained to fight in confined underground spaces, evacuate casualties and clear train carriages.
Berlin has a population of about 3.78 million people.
Its metro — or U-Bahn — runs along a network of about 55 kilometres and 175 stations.
"In the event of tension or conflict, we protect the facilities of the federal government. And this is where they are located," Lieutenant Colonel Teichgraeber told Die Welt newspaper.
"Nothing is simulated down here. The terrain is as it is."
Other locations throughout the city were also used by about 250 soldiers from the Wachbataillon's 2nd and 3rd companies for the week of Bollwerk Baerlin III exercises.
Drills took place at a decommissioned chemical plant in Rüdersdorf, and the "Fighting City", which was a NATO training area in the Cold War, but is now used by the German police.
The drills come as senior European defence figures have been warning about the need to prepare for possible clashes with Russia.
The Bundeswehr said the exercises reflected Germany's renewed focus on national and alliance defence amid rising security tensions in the region following Russian President Vladimir Putin's full-scale Ukraine invasion in February 2022.
Lieutenant General Alexander Sollfrank, who oversees all of Germany's military operations and crisis deployments, has echoed NATO warnings that Moscow could potentially mount a large-scale assault on the 32-member alliance as early as 2029 if its armament efforts persist.
A small-scale attack could be around the corner, he added.
"If you look at Russia's current capabilities and combat power, Russia could kick off a small-scale attack against NATO territory as early as tomorrow," Lieutenant General Sollfrank told Reuters earlier this month.
Hours before the exercises, Germany's defence minister Boris Pistorius warned of sabotage attempts and hybrid attacks by Russia.
He also said it was possible more violent acts could come earlier than predicted.
"Some are saying that it could be envisaged from 2028," he told told Frankfurter Allgemeine Zeitung newspaper.
"And there are even experts who think we might have just lived through our last peacetime summer."
Mr Putin denies aggressive intentions, saying Moscow's 2022 full-scale invasion of Ukraine was defence against NATO's own expansionist ambitions against Russia.
ABC/Reuters
