"Given the catastrophic damage over a period of three decades, it's a wonder anything's working at all, frankly," admits railway historian Tim Doling.
Sitting in a first-floor restaurant above the busy streets of Ho Chi Minh City, I am at the end of an epic 1,000-mile (1600km) journey along the train line he is referring to.
"By 1973, all that was left of the south Vietnamese network was something like 47 kilometres of line running out of Saigon, so the whole thing just ground to a halt," continues the middle-aged British expat, who chronicles the railways of his adopted home.
"Most of the rest of the network was destroyed."
A slim country which narrows at the centre, as if cinched by a belt before bulging at either end, Vietnam appears custom-made for a north-south railway line.
From the hectic capital of Hanoi, close to the border with China, the track hugs the coast of the South China Sea before running slightly inland to leave me in the nation's largest city, formerly known as Saigon.
A tale of construction and destruction, railways were introduced to this corner of southeast Asia by French colonists in the 1880s, after they envisaged an opportunity to capture the rice market, a project beset by poor planning and financial failures.
Years of fighting against occupying foreign forces during the 20th century, culminating in sustained US bombing and sabotage from local guerrilla soldiers, almost signalled the railway's demise.
Rebuilding the ruined network quickly became a political priority in the aftermath of the Vietnam War, as a symbol of reconciliation for a nation partitioned during two decades of instability and conflict.
Remarkably, it took less than two years for a rudimentary line to become operational in 1976.
The rebirth of a route originally completed in 1936 resulted in an unofficial renaming, and it is now colloquially dubbed the Reunification Express.
Revered revolutionary leader Ho Chi Minh did not live long enough to see the end to division in his country, but his legacy endures, particularly in Hanoi - where my journey begins.
Affectionately known as "Uncle Ho", he led the resistance movement against the French during the First Indochina War before proclaiming independence and establishing the Democratic Republic of Vietnam in 1945.
During my visit, red, rectangular posters adorn almost every lamp post to commemorate what would have been his 128th birthday, while seemingly endless lines of schoolchildren queue outside his grey, granite mausoleum, hoping to catch a glimpse of his embalmed corpse which was placed there in 1975, six years after his death.
I leave Hanoi in the darkness of early evening, boarding an overnight train bound for the imperial city of Hue, some 640km further south. The night is spent in a private air-conditioned compartment, consisting of two bunk beds and a small table by the window, complete with vase of plastic flowers.
Walking unsteadily along a narrow corridor at one side of the carriage as we rattle along the uneven rails, I discover not everyone has it so good. Some passengers squeeze into six-bed segments shared with strangers, while those who have purchased the cheapest tickets have to make do with simple wooden benches.
Following a few bounces on the bunk during the night, sunlight streams through the glass as we chug into our destination. Situated on the banks of the Perfume River, Hue was the capital of Vietnam for almost 150 years.
The Unesco World Heritage Site is centred on a vast 19th-century citadel, fashioned after Beijing's Forbidden City and surrounded by a moat and formidable stone walls.
It was the seat of the Nguyen Dynasty - the country's last ruling family - from 1802 to 1945 when the final emperor, Bao Dai, abdicated.
Back on board, I discover the mountainous stretch between Hue and the port city of Da Nang is the line's most scenic.
Standing next to the train door with the window pulled down, I see the partial blur of a railwayman dressed in a smart blue uniform at the side of the tracks signal us on to the winding Hai Van Pass using semaphore.
The train clings to the edge of the cliff, sweeping its way around corners, past secluded coves and deserted beaches while untamed greenery occasionally obscures the misty view of the jagged silhouettes of Da Nang's skyline on the horizon.
As the altitude drops and we pass through the city, emerald-green rice paddies dotted with the conical hats of agricultural workers gradually take over the landscape, alongside water buffalo and palm trees.
Keen for a quick recharge of my batteries after visiting two cities, I alight for a brief stopover in the beach resort of Nha Trang - notable for the towers of Po Nagar, an eighth-century Cham temple - before completing the route to Ga (meaning station) Saigon.
The entire journey takes around 30 hours and I am rewarded with a mix of modern skyscrapers, French colonial buildings and more traditional architecture.
At the heart of the city are the red tiles of the Notre Dame cathedral, adjacent to the general post office, designed by Marie-Alfred Foulhoux between 1886 and 1891, though often credited to Gustave Eiffel.
A fusion of gothic, renaissance and French influences, the cavernous, barrel-vaulted hall, is a popular tourist attraction and presided over by a large portrait of the familiar, bearded man whose name the city now bears.
As evening falls, a sunset cruise along the Saigon River provides a different perspective on my new surroundings, before one final stop the following morning takes me around 50km northwest of the city to somewhere considerably more sombre.
Successfully used as hiding spots and supply lines by the Viet Cong during the Vietnam War, a small section of the elaborate Cu Chi tunnels has been preserved to show the harsh conditions endured.
Shuffling tentatively into the darkness, the stifling heat is close to unbearable. Squatting and hunched, my shoulders span almost the entire width of the confined space, while my head is in constant danger of grazing the unforgiving stone ceiling.
Emerging back into the light above ground, I stumble across a colossal pit at the side of a series of narrow jungle paths. The large indentation in the powdery earth is a B52 bomb crater dating back to incessant American air strikes.
Decades of foreign occupation and international interference have left multiple marks on Vietnam's landscape.
Thankfully, the remarkable railway line running down its spine remains one of them.