Michigan War Studies Review
Reviews, surveys, original essays, and commentary in the field of military studies.
2022-098
17 Oct. 2022
Review by Jonathan Beard, New York City
Lethal Tides: Mary Sears and the Marine Scientists Who Helped Win World War II
By Catherine Musemeche
New York: William Morrow, 2022. Pp. xiv, 304. ISBN 978–0–06–299169–0.
Descriptors: Volume 2022, 20th Century, Female Marine Scientists Print Version

There is a growing literature on the vital, but often forgotten, role of American women in winning World War II. Rosie the Riveter and the millions of other women who built ships and planes feature in dozens of books, but thousands of others worked for the armed services and government agencies in jobs directly tied to the war. In 2017, Liza Mundy wrote Code Girls,[1] telling the story of the thousands of women who toiled in Washington, breaking German and Japanese ciphers. Now pediatric surgeon Catherine Musemeche has revealed how a self-effacing oceanographer helped the US Navy's Hydrographic Office prepare the charts and data books the Marines needed to plan amphibious landings in the Pacific.


Lethal Tides is, first of all, a biography of Mary Sears (1905–97), who for decades overcame pervasive sexism to serve as a scientist at Woods Hole Oceanographic Institution, before and after her work for the Navy. But the book centers on the "Hydro Office" response to the tremendous challenges imposed by the two-ocean war that arrived with Pearl Harbor. Though the US Pacific Fleet had long contemplated a naval war against Japan, it had scarcely considered what would be involved in terms of knowledge of the ocean itself. Musemeche explains, for example, the need to know about drift. When survivors of a sinking ship took to life rafts, or a pilot ditched in the ocean, precisely where would they end up the next day? This was one of the first problems assigned to Sears when she joined the Hydro Office in April 1943. Just a month later, after researching the relevant published literature and reaching out to colleagues at Woods Hole and the Scripps Institution of Oceanography, she submitted her report—The Drift of Objects under the Combined Action of Wind and Current—to her committee. Officials who had doubted the abilities of female scientists were now duly impressed. Throughout 1943–44, the office expanded relentlessly, and hundreds of its new employees were, like Sears, WAVES.[2] One of their most urgent tasks was to prepare for amphibious landings as American forces pushed across the Pacific toward Japan. While the Marines' landings in the Solomon Islands had gone fairly well, the invasion of Tarawa in November 1943 turned into a bloody fiasco.

Tarawa, like so many Pacific islands, was surrounded by coral reefs that were barely submerged at low tide. Many of the Marines' landing craft were stranded on the reefs and over 20 percent of the five thousand men in the first wave were killed.

Many things had gone wrong, but unfamiliarity with the tides was critical. Musemeche describes how Sears and her staff worked to improve the Marines' next series of landings—on Guam, Saipan and Tinian. The Navy improved its pre-invasion bombardments, the Marines got more amphibious tractors that could surmount reefs, and the Hydro Office provided better intelligence. Though their charts and forecasts kept getting better, there were limits to how much science could help. Before the invasion of Iwo Jima, the office provided many warnings about the beaches, but they were ignored. The Navy had decided to capture the island no matter what. Iwo Jima, with its loose volcanic-sand beaches, proved even bloodier than Tarawa. The book goes on to the fairly routine landings on Okinawa and the endless preparations to invade Japan itself. An epilogue chronicles Sears' postwar career at Woods Hole.

Musemeche skillfully captures Sears's constant, simmering battle against her sexist superiors, first in academic oceanography and then in the Navy; the former recognized her abilities but restricted her participation in survey voyages, while the latter delayed her deserved promotions in rank.; the latter recognized her abilities but restricted her participation in survey voyages and deserved promotions in rank. The author also clarifies how the Hydro Office gathered information on the Pacific and its islands—much of it in obscure journals and Japanese documents—and disseminated it to Navy and Marine leaders.

Musemeche sometimes overstates things: it is not true, for instance, that "German U-boats had come dangerously close to dooming the British fleet and winning the war" (78). But she gets most of the military history right. Ironically in a book that wears its feminism on its sleeve, much attention is paid to fashion. Main Rousseau Bocher, better known as Mainbocher, had designed the wedding dress Wallis Simpson wore when she married the Duke of Windsor. In 1942, when the Navy created the WAVES, it commissioned him to design their uniforms. His outfits were a great success, even serving as a recruiting tool for the Navy. Several women who worked in the Hydro Office recalled them with great affection. It seems unlikely that Mary Sears cared very much.

The publishers have enhanced Lethal Tides with twelve pages of photographs and charts illustrating the work of the Hydro Office and the main characters in the narrative. There are also endnotes (sadly, not footnotes) and an index. Readers wanting to know more about the contributions of both women and scientists to the American war effort in World War II should read Lethal Tides.

[1] NY: Hachette.

[2] "Women Accepted as Volunteer Emergency Serviceworkers."

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