Because of the selective way popular historical narratives are communicated, the success of the Allied amphibious landing on the beaches of Normandy during World War II seems to have occurred spontaneously thanks to meticulous planning and impeccable execution. Sure, there were Allied casualties. That was to be expected. But they still pulled off a military masterstroke that allowed them to conquer Hitler’s Nazi war machine.
Thing is, there were many earlier attempts at landing troops on hostile shores and very many of them were out and out disasters. The only redeeming factor for all of them was that the people who ran the war, the admirals and their staff, learned valuable lessons with each bloodbath. One of the most important details not immediately apparent during the planning stages of amphibious invasions was the critical role oceanographic data played in determining a landing’s outcome. Long before marines stormed the shores of Normandy, a tiny island in the middle of the Pacific Ocean called Tarawa demonstrated just how important something as seemingly mundane as the tide could turn a perilous operation into a bloodbath.
Lethal Tides: Mary Sears and the Marine Scientists Who Helped Win World War II by Catherine Musemeche tells the story about one of the most important unsung heroes of the Pacific War, Mary Sears, who was an oceanographer with the Navy Hydrographic Office during the Second World War.
Born and raised in Wayland, Massachusetts, Sears graduated from The Winsor School in Boston. She attended Radcliffe College, receiving a bachelor’s degree in 1927, a master’s degree in 1929 and a Ph.D. in zoology in 1933. During her graduate studies at Harvard University, Sears worked with Henry Bigelow, a founder and the first director of the Woods Hole Oceanographic Institution. She worked summers as a planktonologist, one of the first ten research assistants to be appointed to the staff at the Institution, and was appointed to a year-round position as planktonologist in 1940.
It was not easy. According to Musemeche,
Being a woman had thus far kept Sears far from the action, apart from the most important activity of her career… Instead of finding plankton or protozoa, she found only frustration.
In large part, this was due to the social climate at the time in which women were excluded from many professions outside of the accepted ones such as secretaries, nurses, or teachers, a reality summed up succinctly in Lethal Tides
Opportunities for women scientists in the 1930s were so limited that Sears had been fortunate to land any job at all. The fact that she had chosen a field where there was no demand for women made her position all the more precarious.
With the outbreak of World War II, Sears was commissioned a Lieutenant Junior Grade in the United States Naval Reserve (Women’s Reserve), better known as WAVES (Women Accepted for Volunteer Emergency Service), a women’s unit of the Navy in 1943. Subsequently, she organized and headed the Oceanographic Unit of the Navy Hydrographic Office, working with Roger Revelle and a band of talented scientists. Together, they prepared oceanographic reports for planning of events in the Pacific, including charts that were drawn on handkerchiefs that were navigation aids carried by soldiers.
By 1944, the Joint Chiefs of Staff expanded Sears’ responsibility to include management of over 400 people. Her unit provided intelligence to the Navy that included analysis of tides, surf heights, and other oceanic metrics to give the Navy a strategic advantage.
Sears was not immediately successful. As with her time at Harvard, gaining respect and support from her superiors did not come easily for her or for the Oceanographic Office, in general. The stereotypical prejudices you’d expect from “men of action” against any possible contribution by bookish scientists were in play. Eventually, the war’s planners learned their lesson but only after learning the hard way.
It took a veritable disaster to really change the thinking of top Navy officials. The Battle of Tarawa illustrates the perils of ignoring or marginalizing the information oceanographers could easily have provided. Specifically, naval planners took for granted that they knew what tide levels would be on the shores surrounding the island atoll during the time of invasion. It was a dangerous assumption, particularly when taking into account the coral reefs that ringed the island. Yet, with the brand new Higgins boat at their disposal, the Marines were confident that getting their boots in dry sand would not be a problem. Advancing on entrenched Japanese positions would be where the danger lay, as expected.
Reality proved the complete opposite.
As Sherrod searched the shoreline for some sign of the preceding waves of boats, he swallowed hard. He couldn’t pick out a single Higgins boat. All he could see on the beach were a few scattered amphibious tractors. Where were they? The mystery was solved when a naval officer in a command boat pulled up alongside and yelled, “You’ll have to go in right away, as soon as I can get an amphtrack for you. The shelf around the island is too shallow to take the Higgins boat.”
The boats carrying the soldiers were stranded too far from the coast. The troops would have to wade the distance in water chest high. The results were as bloody as expected.
We’d watch these lines of marines climb out of the Higgins boats as they worked up on to the reef, and then try to walk ashore and occasionally we’d see a man disappear. Then, maybe two or three menaway another man would disappear, and they would just drop in the water. We couldn’t see the blood but we knew what was happening. These men were being picked off by the machine guns because we could see the machine gun bullets hitting the water like raindrops.
It was carnage.
Almost any other week, almost any other day, the marines would have gotten the minimum four feet they needed to clear the reef, but what they got on November 20, 1943, was closer to three feet. Instead of sailing to shore, the bottoms of the Higgins boats scraped across the coral reef and stopped. No boats crossed that barrier the morning of the assault, and none for the next forty-eight hours.
A phenomenon called a neap tide had kept the tide from rising to the normal level of four feet. While it could be considered a rare event, it was one that could have been predicted by the oceanographic group.
Even though, Allied troops eventually took the island, the number of casualties made it a pyrrhic victory. Roughly 5,000 soldiers attempted the amphibious landing. Of those, 1,027 were killed and an additional 2,100 were wounded. An estimated 300 soldiers were picked of simply trying to make it from one side of the barrier reef to the other. Others died while on shore, waiting for reinforcements, most of whom were already dead or injured in the water. When the campaign was studied by military strategists, the greatest error had been the way planners misjudged the tide. In the end, public outrage spawned Congressional hearings as to how the early stages of the battle could go so wrong.
Admiral Nimitz and his officers came to the conclusion they should have reached long before.
If the navy were going to avoid another Tarawa, they would have to study the ocean like never before. And they would have to do so in the midst of a war that would not wait for them to catch up.
Ultimately, the battle provided the Navy with the impetus to lean on Sears and her Oceanographic Office for reports and other forms of intelligence. Not just for amphibious attacks but for all elements of warfare that took place in the ocean.
While most people are aware of the way scientific discoveries like radar and the nuclear bomb can pave the way to victory during a war, Lethal Tides captures the importance of basic science in conducting a successful campaign. The work done by Sears and her fellow oceanographers proved pivotal to naval campaigns during and after World War II. The Oceanographic Office demonstrated how something as mundane as the height of a continental shelf or the location of coral reefs made the difference between tens of thousands of dead American soldiers and military glory.