Below is an excerpt from the NYT about the history of Western meddling in Iran, with a sub-theme (reflected in the title) that is inessential to basic understanding of the politics and motivation of all parties.
The Persian Complex - New York Times
[...]
We tend to forget that Iran's insistence on its sovereign right to develop nuclear power is in effect a national pursuit for empowerment, a pursuit informed by at least two centuries of military aggression, domestic meddling, skullduggery and, not least, technological denial by the West. Every schoolchild in Iran knows about the C.I.A.-sponsored 1953 coup that toppled Prime Minister Mohammed Mossadegh. Even an Iranian with little interest in his or her past is conscious of how Iran throughout the 19th and 20th centuries served as a playground for the Great Game.
Iranians also know that, hard as it may be for latter-day Americans and Europeans to believe, from the 1870's to the 1920's Russia and Britain deprived Iran of even basic technology like the railroad, which was then a key to economic development. At various times, both powers jealously opposed a trans-Iranian railroad because they thought it would threaten their ever-expanding imperial frontiers. When it was finally built, the British, Russian (and American) occupying forces during the Second World War made full use of it (free of charge), calling Iran a "bridge of victory" over Nazi Germany. They did so, of course, after Winston Churchill forced the man who built the railroad, Reza Shah Pahlavi, to abdicate and unceremoniously kicked him out of the country.
Not long after, a similar Western denial of Iran's economic sovereignty resulted in a dramatic showdown that had fatal consequences for the country's fragile democracy and left lasting scars on its national consciousness. The oil nationalization movement of 1951 to 1953 under Mossadegh was opposed by Britain, and eventually by its partner in profit, the United States, with the same self-righteousness that today colors their views of the Iranian yearning for nuclear energy.
[...]
A few other worthwhile sources of information: