In 1975, the US cut diplomatic ties with Hanoi after the end of the Vietnam war (also called the second Indochina war), which left more than a million Vietnamese and more than 58,000 Americans dead. US officials and allied South Vietnamese famously fled Saigon (now Ho Chi Minh City) in the biggest helicopter airlift in American history. Now, though the country remains a highly repressive, nominally communist state, it has become one of Washington’s dearest friends in Asia.

The US navy pays regular port calls in Vietnam. US President Barack Obama lifted the ban on sales of lethal arms to Hanoi, which had been in place since the end of the war. Annual trade between the two nations is worth roughly US$45 billion. When the head of Vietnam’s Communist Party visited Washington last year, he made the rounds of official meetings, think tank talks and private briefings like a conquering hero.

Such a swing in relations might seem unusual. Since the Vietnam war introduced Americans to the country, journalists, historians and many foreign leaders have viewed it through a narrow prism: Vietnam is a country repeatedly invaded by foreign powers, from imperial China to colonial France to the US; it is a country with a tenacious people, whose identity has been forged by fighting invaders.

Vietnam’s foremost heroes, such as the 18th-century emperor Quang Trung, and Ho Chi Minh, are those whose wars forced foreign powers out.

But as Christopher Goscha shows in this groundbreaking book, Vietnam has always been a far more complicated place – politically, strategically, economically and culturally – than this image of a country of stubborn, united fighters would suggest. He manages the difficult task of showing Vietnam’s complexity without losing the reader with too much detail.

Goscha understands that Vietnam is a land long coveted by major powers – it is a narrow spit of coast with fertile deltas, astride one of the most important trade routes in the world. But it has also been a major regional power itself. At times, it has fought back against foreign powers, but at other times it has sought diplomatic alliances, or welcomed migrants into what is a very ethnically and religiously diverse country.

Vietnam has enjoyed periods of unity, but even the Vietnamese Communist party was more divided than most outsiders realised. And today, Vietnam’s unity has serious fractures.

Goscha has provided quite simply the finest, most readable single-volume history of Vietnam in English. He takes on some persistent myths about the country. First, that Vietnam has been constantly preyed on. In the period before Western powers colonised the region, Southeast Asia’s own empires constantly colonised each other. A series of Vietnamese empires conquered parts of modern-day Laos and Cambodia between the 15th and 19th centuries, while alternately fighting and placating China’s rulers, who saw Vietnam as a vassal state.

Second, Goscha shows that Vietnamese dynasties were actively modernising the country before French colonisation began in the 19th century. The Nguyen dynasty was establishing new tax and irrigation systems, new schools and a modern bureaucracy when France declared its rule over Indochina.

Under the Nguyens, the French and the two governments of South and North Vietnam, the country was hardly monoethnic, though the pictures most Americans saw of Vietnam were of ethnically Viet people. Vietnam, as Goscha argues, has long been influenced not only by the majority ethnic Viet and by Chinese Confucian culture, which spread south over centuries, but also by a far broader range of cultures and peoples.

During the French and American eras, Paris and Washington made much of the need to protect oppressed religious minorities – primarily, Catholic Vietnamese – as a reason for military involvement in Indochina. (This was not the primary driver of US policy, which was based on strategic calculations, but it was an effective rhetorical device.) The flight of up to one million North Vietnamese, many of them Catholics, to the south after the country was divided in 1954, fleeing in boats provided in part by the US navy, captured the imagination of Americans and Europeans.

Goscha also adds to the growing pile of evidence showing that virtually all of the policy mistakes made by the US during the Vietnam war had been made, in almost all the same ways, by France in its Indochina war between 1946 and 1954. Of course, the US military dramatically stepped up the asymmetrical warfare when joined in the Vietnam war, as Goscha notes. Its bombing campaigns were of a very different scale. Yet US policy makers insisted then – and some still insist – that they acted differently, that America was not a colonial power in Vietnam and the US could succeed, they thought, by working with local nationalist leaders.

Between 1975, when the country was reunified at the end of the war, and the early ’90s, Vietnam’s already battered society struggled through more upheavals, ones little understood outside the region. The Vietnamese military invaded Cambodia and removed its former ally the Khmer Rouge in 1979. Hanoi fought a border war with China in the same year. Then the country struggled through decades of grinding poverty. The Vietnam war left the country having to rebuild its entire infrastructure, and the legacy of the war lingered for 15 years, as the US imposed sanctions on Hanoi.

The country embarked on economic reforms in the late ’80s and early ’90s, at the same time as the end of the cold war allowed the US, and Vietnam’s Southeast Asian neighbours, to restore diplomatic and economic ties to the country. These reforms fostered two decades of growth, and transformed Ho Chi Minh City into a burgeoning Asian megacity.

But reforms that have opened up parts of the economy have also left staggering amounts of corruption and debt in state enterprises. The Communist Party’s leadership remains opaque, and the divisions – between supposed reformers and supporters of harsh, one-party rule – are hard to discern.

Vietnam’s economy is moving ahead but the next step forward for Vietnamese politics remains hard to imagine.