Benjamin Franklin was far and away the most famous American when he went to France to wheedle help for the newborn American nation, which was having a very grim time of it when he got there late in 1776. Stacy Schiff’s wholly engrossing A Great Improvisation: Franklin, France, and the Birth of America (Henry Holt and Company, 480 pages, $27.50) casts the reader ashore on the French coast alongside Franklin, and together they learn to negotiate a city and a society at once magnificent and sordid, generous and dangerous (and, of course, so sexy that Americans have never quite gotten over it), and, above all, just as unfamiliar to eighteenth-century Franklin as it is to twenty-first-century us. If he couldn’t unravel its mysteries quickly enough, his brand-new nation might very well go under. Schiff’s introduction suggests the stakes:

“America was six months old; Franklin was seventy years her senior. And the fate of that infant republic was, to a significant extent, in his hands. He sailed to France not for self-emancipation, as Americans have since, but for that of his country. Congress had declared independence without any viable means of achieving it; the American colonies were without munitions, money, credit, common cause. In the spring of 1776, foreign assistance had been debated as hotly as was independence. The two discussions were inextricably bound; to many the former qualified as the more palatable proposition. The best orator in Congress argued persuasively that a declaration of independence was a necessary step for securing European aid. In that light the document’s name constituted a misnomer. It was drafted as an SOS.

“‘If I call Europe, what number do I call?’ Henry Kissinger asked in the 1970s. In the 1770s the answer was obvious. Especially if you had a grievance with Britain, you called Versailles. How you did so was equally obvious.…You summoned the one man in the colonies possessed of that brand of sleek charlatanism known as social grace, the only one of the Founding Fathers familiar with Europe. Few Americans could have risen to Paris’s diplomatic or conversational agenda, and even fewer could have done so with the requisite wit, in a language that approximated French. Whether Franklin could succeed in his mission was another question. In the annals of diplomacy his was the original one. Franklin was charged with appealing to a monarchy for assistance in establishing a republic.”