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Wolfe’s Secret Weapon

Time Magazine (09/29/2002)

By Leon Jaroff

When British General James Wolfe embarked down the St. Lawrence River toward his epochal 1759 battle against French forces on the Plains of Abraham, he knew he faced some formidable obstacles. As his naval counterpart, Admiral Charles Holmes, described it, Wolfe had to contend with “the distance from the landing place … the impetuosity of the tide … and the darkness of the night.”

Modern historians have argued that luck played a large role in Wolfe’s overcoming those obstacles, winning the battle—in which he was killed—and ending French rule in Canada. But an American astronomer, writing in the current William and Mary Quarterly, has demonstrated that Wolfe used the best scientific knowledge available at the time to achieve victory. This feat, according to Donald Olson, who teaches a course called Astronomy in Art, History and Literature at Southwest Texas State University, was one of intelligence as well as arms.

Olson first became interested in Wolfe’s strategy in 1996, when he read a popular account of the events leading to the general’s victory. The narrative described Wolfe’s flotilla of small boats moving stealthily down the St. Lawrence toward the French forces on a “moonless night.” As it happens, Olson is fascinated by the moon and its impact on history. He has previously shown, among other things, how the moon’s orbit influenced such events as the Boston Tea Party and the World War II battle for the Pacific atoll of Tarawa.

Was that night in 1759 truly moonless? Just to check, Olson used a series of computer programs that can duplicate the night sky at virtually any point on Earth at any time, on any date in any year to locate the position of moon on the night of Sept. 12-13, 1759, the eve of the Quebec battle. The historical account Olson had read was wrong. A fairly bright moon—54% illuminated—remained in the eastern sky during Wolfe’s entire river transit, lighting the way for his boats. Yet the French sentries, looking upriver, could see little in the darkness.

That bright moon affected Wolfe’s victory in other ways. How had he timed the passage of his flotilla so that it traveled downstream from the British anchorage to Anse au Foulon, arriving in time for his troops to disembark, scale a steep cliff in darkness and surprise the French on the Plains of Abraham at daybreak? It was a formidable task. Influenced largely by lunar gravity, currents on the St. Lawrence flow downstream—the ebb tide—at varying speeds for more than seven hours, are briefly stilled and then flow upstream for five hours, in a repeating cycle. These reversals vary not only with lunar phases but also with the position of the sun in various seasons and the distance of the moon from Earth.

With his computer programs, Olson discovered that on the evening of Sept. 12-13, 1998, all conditions would be identical to what they had been when Wolfe set forth. Grasping the opportunity, the scholar traveled to Canada with several colleagues and students and borrowed a launch equipped with a global positioning system from the Canadian Department of Fisheries and Oceans. At 2 a.m. on Sept. 13, as the ebb current began picking up speed, the group cast off and drifted downriver, just as Wolfe and his troops had done. And precisely two hours and 7.6 nautical miles later, shortly before the sky lightened, they passed Anse au Foulon, where Wolfe’s troops had disembarked.

The results confirmed that Wolfe’s Royal Navy advisers had accomplished the impressive task of determining the timing of the tides and the average speed of the current, which varied widely with the configuration of the river. That feat enabled the invaders to calculate the time it would take for a flotilla to traverse the 7.6 nautical miles to its destination. They had also picked the only ideal night that month for the foray. Had Wolfe begun his operation the following night, his troops would have arrived at the foot of the cliff just as dawn was breaking, easy targets for the French.

“It was, of course, officers of the Royal Navy who sorted out the tidal patterns in the St. Lawrence,” says Olson, “but Wolfe at least had the perspicacity to use the best scientific data and analysis available.” And that enabled the general to stage the most important lunar landing on the North American continent, and win an empire at the cost of his life.