Since Russia's invasion of Ukraine began, one striking aspect of the war has come to the fore: The critical role played by Ukraine's railway system.
The nation's extensive network of freight and passenger lines is at once a life-saving humanitarian resource, a tool of diplomacy - and a potent weapon of self-defence.
On Mar 17, Oleksiy Arestovich, an adviser to Ukrainian President Volodymyr Zelenskyy, called for a "total rail war" against the invading troops - simultaneously keeping supply lines to the front open and disrupting any in use by the Russians.
Some seem to have taken this call to heart.
Oleksandr Kamyshin, the chairman of national carrier Ukrzaliznytsia (or Ukrainian Railways), implied in an recent interview that rail workers in neighbouring Belarus had helped Ukraine's war effort by sabotaging rail links towards the border, to impede the flow of Russian troops and military equipment - a claim later repeated in a tweet from an adviser to the Belarusian resistance.
This suggestion that railway workers are actively hindering the Russian advance came one week after the Polish, Czech and Slovenian prime ministers all chose to travel by train to Kyiv for talks with President Zelenskyy, a reflection of their confidence in the network's safety.
Since the invasion began in late February, Ukraine's railway system has been a coveted prize for Russian forces, whose efforts to control logistics hubs in major cities such as Kharkiv and Kyiv have been foiled by stiff local resistance.
Instead, Ukrzaliznytsia has remained in Ukrainian hands, and its fleet has functioned as the main means of escape for millions of civilians fleeing to the relative safety of western Ukraine and the countries beyond the nation's borders.
At the peak of the refugee migration in early March, 190,000 rail passengers a day travelled westward in free evacuation trains.
In some ways, the current fate of Ukraine's railways reflects shifts in the country as a whole: Links with Russia and Belarus are being severed while those with countries to the West are being strengthened.
Polish volunteers have even attempted to revive defunct 19th-century lines crossing into Poland in an effort to assist evacuations.
It's a system that has so far proved remarkably resilient and adaptable, continuing to move refugees, humanitarian supplies and troops around the country - even stepping in to serve as urban transit.
With war conditions in Kyiv making it impossible to run metro services between the two banks of the River Dnipro, the national railways opened a cross-river link across a bridge in a southern section of the city relatively safe from bombardment. On Mar 29, suburban rail services also resumed in the heavily shelled city of Kharkiv.
For rail staff and refugees alike, the crush of passengers created extremely difficult conditions.
When Serhi and Ira, who asked not to have their full names published, evacuated Kyiv with their one-year-old son Petro, they were only able to get on a train because an engineer allowed the family to ride in his cramped driver's compartment for the 13-hour trip to the western city of Lviv.
"That's five hours longer than usual at peacetime," Serhi said in an interview.
"We didn't sleep the whole night - my wife and I took turns sitting on the seat, depending on who was holding the sleeping kid. But we took no notice of the conditions, we were just grateful to the locomotive driver for his kindness and understanding. He has a huge heart."
For people who just months before were used to relatively fast, efficient travel aboard one of Europe's largest rail networks, the shift to wartime conditions was a shock.
"It's challenging to compare journeys in peacetime and now," said 25-year-old Alisa Paliy, a systems analyst who left Kyiv in early March. "In the evacuation trains, the cars are full of chaos, fatigue and sadness in people's eyes."
Many families travelled with small children and pets; riders in crowded cars were forced to stand in aisles and vestibules throughout the journey.
"I caught myself thinking of getting off the train and returning home several times," Paliy said. "But without the trains running - especially the free ones - it isn't easy to imagine how so many people could have got to safer regions."
The number of refugees riding the rails has thinned since the peaks of early March, with daily ridership dropping to 80,000 by the end of the month.
On Mar 20, Ukrzaliznytsia announced that it would return to selling tickets. While the many evacuation services still heading westwards - with timetables publicised daily in Ukrainian media - will remain free, regular fares on other routes will resume.
This exodus has been managed under intense pressure.
Not only have stations, bridges and key rail links faced shelling - in the case of the besieged south-eastern port of Mariupol to a point beyond repair - railway management have also become targets, obliging Ukrzaliznytsia chairman Kamyshin and his colleagues to abandon their Kyiv offices and take to the rails themselves, at times in their own single-carriage command centre.
This allows them to both protect themselves by staying mobile and visit stretches of the network that need immediate repair and support.
Meanwhile, the staff's organisation has changed to prioritise wartime needs, with some staff members returning from office jobs to the rails.
Former conductor Vadym Kuksa, 53, is a Soviet Army veteran who began working for Ukrzaliznytsia in 1988. When the war began, he was serving as the chairman of the railway workers' union in the city of Poltava; he immediately volunteered to return to work as a conductor on evacuation trains.
"The specifics of the work have changed completely," he said.
"First of all, I don't bar anyone from entering a car. The cars' normal capacities range from 36 to 52 passengers depending on the model, but during the peak of the evacuations they carried as many as they could fit. There were people everywhere - in the corridors, in the racks - so we could evacuate anyone who wanted to leave."
Conditions in the evacuation trains can be tense. At night, the cars travel in darkness to deter attack, and the heavily laden trains have been running at reduced speeds and stopping frequently when air raid sirens sound.
"People are worried, nervous, they require much more attention from staff," Kuksa said. "We deal with people in shock and nervous breakdowns, and sometimes we have to provide psychological and medical aid."
Keeping trains running has also proved dangerous. At least 40 rail staff have been killed and 41 injured on duty, according to Kamyshin.
Kuksa said that in one case, a train conductor was killed when an evacuation train hit a mine prior to picking up passengers. These alarming numbers are still relatively low when you consider that Ukrainian Railways staff - now thinned out as many female employees have been evacuated westward - numbered about 250,000 before the war, making it one of the country's largest employers.
"In my opinion, railway workers play a significant role in our victory," Kuksa said. "Ukrzaliznytsia belongs to the critical infrastructure sector and is a strategic enterprise of Ukraine, especially in wartime. Perfect discipline has always been its distinctive feature."
Railroad workers may not be officially members of the military, but they do wear uniforms - though not, Kuksa noted, bulletproof vests.
"We are called 'iron people'," he said, using the Ukrainian word for railroad worker, zaliznychnyk (literally "iron road man"). "And that's for a good reason."