At its height under Darius I, the Achaemenid Empire governed 40 to 44 percent of everyone alive on Earth, a share no later empire, including Rome, would ever match. Twenty-five centuries later, its heirs run a nuclear program that dominates world headlines. What happened in between is the subject of this book.

This is one continuous history of Iran, from Cyrus's conquest of Babylon in 539 BC to the Islamic Republic of today, told as a single unbroken story rather than ancient Persia in one book and modern Iran in another, following empire, faith, and nation through five political systems and one revolution.

Inside, you'll find:

• How a 1901 oil deal led to a 1953 coup. The Anglo-Persian Oil Company paid Iran only 16 percent of its profits from Abadan, then the world's largest refinery - the grievance Mohammad Mossadegh rode into office on, and that a CIA- and MI6-backed coup later reversed.
• Why Marathon nearly didn't go Greece's way. A Persian force of roughly 25,000 to 30,000 men against some 10,000 Greek hoplites, and why Herodotus's other numbers, like the 2.5 million he gives Xerxes a decade later, don't survive contact with logistics.
• A population that grew past 85 million. From roughly 19 million at Reza Shah's 1925 coronation, through a state-encouraged baby boom, to one of the steepest fertility declines anywhere in the 1990s.
• A railway built without a single foreign loan. The 865-mile Trans-Iranian Railway, with more than 4,100 bridges and 224 tunnels, finished in 1938.

No prior knowledge of Persian or Iranian history is assumed, and no side of Iran's current politics is argued for; where historians disagree, this book says so rather than picking the cleaner story.

Three thousand years, one country, told straight through.