As I trudge through the jungle, I flinch at the sharp sound of AK-47s being fired at a nearby shooting range.
'And on your left, another crater,' says Vietnam guide An Dung, leading us over the pitted, hardened red earth and through a eucalyptus grove. The crater was made by a B-52 bomber. This is Cu Chi, about 20 miles outside Ho Chi Minh City where, during the Vietnam War, Viet Cong guerillas hid from the Americans in a 200-mile network of tunnels.
Battle ground: Hue's Imperial Citadel was seized from the Americans in 1968
US troops withdrew from the country 40 years ago, yet there are still so many reminders of the war, including these tunnels. While four decades ago Westerners who arrived in Saigon (since renamed Ho Chi Minh City in honour of the iconic North Vietnamese communist leader) were armed with semi-automatic rifles, they now carry the latest cameras, and factor 30 sun cream is the only defence you need.
The former battle sites of this country, once so bitterly divided between the communist North and the anti-communist South, are popular tourist destinations.
From Ho Chi Minh City in the south to the northern capital Hanoi, the Vietnamese are proud to display their victory over mightier forces during what they call the American War.
Clambering into the Cu Chi tunnels is a living history lesson. The manhole-size entrances, hidden under fallen palm fronds, have been widened for the tourists. It's a good job too - I wouldn't be able to get in otherwise. The Vietnamese are petite.
It's total darkness underground, and I have to feel my way along the clay walls. Sometimes, the ceiling is so low I have to crawl to reach the next tiny chamber. It is like being incarcerated in a hard, cold box while wearing a blindfold.
The Viet Cong hid down here for months. I stayed for ten minutes before I fled for the exit, climbing up towards the light and the silhouette of an M41 tank captured from the Americans. Such spoils litter the jungle.
Reminders of conflict: A guide emerges from a Cu Chi tunnel, built by the Viet Cong and famous for its tiny dimensions
Even above ground, life was pretty tough for the guerillas. An Dung fed me mashed tapioca root with salt and sugar - the Viet Cong's staple diet. It tasted like cold porridge, only worse.
As I ate, more gunfire cracked through the trees. It was coming from the range at the tunnels, where tourists can select a semiautomatic weapon of their choice and shoot at imaginary foes. I had reached Cu Chi after taking an hour-long speedboat journey along the Saigon River from Ho Chi Minh City.
In the throbbing capital city, the main sound isn't gunfire but the 'fut fut' of more than ten million mopeds swarming around the streets. Each bike carries two, three or four people, including babies. The riders look like ninjas as scarves cover most of their face to keep out the fumes.
I had my own skirmishes with these road warriors - there are no crossing points so our guide issued the following advice: simply step slowly into the stream of two-wheeled traffic, and don't stop or make any sudden movements, otherwise you will just jump into the path of another bike. No one stops for pedestrians - the motorbikes just go around you. It's terrifying.
At least it was easy to find my way around. Vietnamese cities have what can only be called 'zoned shopping'. All the shops in the same street sell a single item or service.
Bright outlook: Women carry goods to market in Ho Chi Minh City
For example, the street where my hotel was located sold only mobile phones. The next street sold plastic flowers. The next, spare parts for mopeds. Each street is named after what it sells. So when I needed a camera battery, I just had to ask for camera battery street. Simple.
In Ho Chi Minh City, it's not easy to forget the war. In the courtyard of the War Remnants Museum, I posed in front of captured American tanks, camouflaged reconnaissance planes and a Huey helicopter.
The Historical Truths and Aggressive War Crimes galleries inside showed the human cost of conflict, with photos of families fleeing US attacks.
The Tet Offensive by Viet Cong forces, the My Lai massacre and the fall of Saigon are all detailed here. The giant faded casualty charts are chilling. There's no attempt at objectivity. This is a portrait of the war as seen through communist eyes. There's even a wall naming and shaming those US soldiers who committed the so-called crimes.
The Americans aren't Vietnam's only recent invaders. Before them, the French were the country's colonial masters, and they planted the huge trees that provide welcome shade along Ho Chi Minh City's wide boulevards.
All aboard: Children get a lift to school in Ho Chi Minh
They also left behind a cluster of ornate buildings, including a grand opera house with a sweeping staircase, a hotel de ville with crystal chandeliers (it's now the People's Committee Building), and a cathedral named Notre Dame.
I spent an evening looking over what remains of Old Saigon from the rooftop bar of the Caravelle Hotel, where foreign journalists stayed during the war.
I tried to imagine what it was like when the sound above wasn't whirring fans that help keep customers cool but the rotors of US helicopters, and the sound below not that of mopeds but rumbling tanks.
History lesson: Dea discovers more about the brutal 20th century clash at the War Remnants Museum
Afterwards I took a taxi back to my hotel, and Hotel California by The Eagles blasted out from the car radio, while a golden Buddha figure bounced up and down on the driver's dashboard.
Along the way we passed women carrying bamboo poles that held baskets of produce. I also counted the golden tips of pagodas, and understood why people can't help but fall in love with this land.
During my trip, I followed the invaders' route northwards, towards central Vietnam, the region that saw the most ferocious fighting.
Fortunately, these are more peaceful times and on my arrival at the Pilgrimage Village hotel on the outskirts of Hue, the only sound was the pit-pat of flip-flops on the stone tiled pathways around the lush gardens. At night, there was the squawk from the nearby karaoke bar (the Vietnamese are devotees).
But even in this prosperous city crowded with modern office blocks, the American War is still evident. I took a cyclo (bicycle rickshaw) across the Perfume River to Hue's vast Imperial Citadel, encased by a moat and eight-mile ring of thick ramparts. In the early 19th Century, the Imperial Enclosure and Forbidden Purple City within them were the centre of Vietnam's royal court.
During the Tet Offensive in 1968, the communists seized the Imperial Citadel from the Americans and defiantly raised a giant National Liberation Front flag over it. It flies there today, a symbol of resistance.
The imperial buildings are still pock-marked as a result of bullets and shell fire, and the process of reconstruction, which has been going on since the American tanks left, is due to be finished by 2025.
I spent a day walking between half-ruined temples, a royal theatre, a pagoda on an island surrounded by a lake, the emperor's reading room and yet more fine museums. Further north, in Hanoi, even the cells that held American prisoners have been turned into a museum.
Taking aim: A tourist tests an AK-47 at the firing range near the Cu Chi tunnels
If you believed the displays at Hoa Lo Prison, you would think it was a former holiday camp - there are examples of starched shirts worn by US troops, their fine leather sandals and even their half-smoked cigarettes.
The PoWs ironically nicknamed it the Hanoi Hilton because of the appalling conditions in which they lived. US Senator John McCain was held here after his aircraft was shot down over the city's Truc Bach Lake and he claims to have been tortured. Nevertheless, there's a statue dedicated to him where he was pulled out of the water.
However, there are plenty of peaceful pursuits too, and an early morning walk around the Hoan Kiem Lake is recommended. As the mist rises, workers do t'ai chi classes and old men sit down for a game of chess close to a scarlet bridge that leads to a temple.
One night, I took in a show at the Water Puppet Theatre. Originally staged in paddy fields and lakes, the puppeteers wade waist-deep into water while working dozens of painted balsa-light puppets on long wooden poles, making them splash, skim and dance. The puppets act out Vietnamese legends with the help of a live band playing traditional instruments.
There was conflict in the show - the dragon seemed to have a fight with the fairy, and the tigers were definitely attacking the farmers. But after what I'd seen elsewhere in this country, this was playful stuff.
My trip to Vietnam had not just taken me to another country - it helped me understand a war I only vaguely remembered from my childhood. It showed me the scars of conflict. It made me think.