WWI USS San Diego Findings

A German mine sank the US Navy armored cruiser
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by Mass Communication Specialist 2nd Class (SW/AW) Mutis A. Capizzi, Naval History and Heritage Command

 USS San Diego (Armored Cruiser No. 6) photographed Jan. 28, 1915, while serving as flagship of the Pacific Fleet. U.S. Navy Photo courtesy of Naval History and Heritage Command

USS San Diego (Armored Cruiser No. 6) photographed Jan. 28, 1915, while serving as flagship of the Pacific Fleet. U.S. Navy Photo courtesy of Naval History and Heritage Command

WASHINGTON, D.C. – After a two-year study into what sank the World War I cruiser USS San Diego (ACR-6), the US Navy announced its findings.

Alexis Catsambis, Ph.D., of the Naval History and Heritage Command’s Underwater Archeology Branch, based at the Washington Navy Yard, led the project and chaired a panel discussion for media at the American Geophysical Union’s (AGU) Fall Meeting. Although the original court of inquiry believed the explosion that sank the 500 foot armored cruiser was caused by a mine, later speculation raised the theory that it might have been a torpedo.

After examining new survey data, additional archival research, computer impact and flooding models, the area of the ocean floor in which the wreck rests, and other elements related to the ship’s loss, Catsambis announced that research team believed the explosion’s cause was a mine. In fact, they believe it was one of two types of mines laid by German submarine U-156.

 ATLANTIC OCEAN (Sept. 11, 2017) – U.S. Naval Academy (USNA) Midshipman 1st Class Nolan Brandon, Ken Haulsee, a graduate student at the University of Delaware, and Peter Barron, a laboratory technician at the University of Delaware, left to right, lower an autonomous underwater vehicle into the water in order to take sonar data on the wreck of the World War I-era armored cruiser USS San Diego (ACR 6), Sept. 11. Members from the Naval History and Heritage Command, Naval Surface Warfare Center Carderock Division, the University of Delaware, the Office of Naval Intelligence, and a USNA midshipman started surveying the shipwreck to gain scientific insight, historical clarity, and in preparation for the 100th commemoration of the vessel’s sinking. The project started with a side-scan sonar and bathometric survey. San Diego was believed to have been sunk off the coast of Long Island in 1918 by a German submarine. U.S. Navy photo by Mass Communication Specialist 1st Class Eric Lockwood/Released

ATLANTIC OCEAN (Sept. 11, 2017) – U.S. Naval Academy (USNA) Midshipman 1st Class Nolan Brandon, Ken Haulsee, a graduate student at the University of Delaware, and Peter Barron, a laboratory technician at the University of Delaware, left to right, lower an autonomous underwater vehicle into the water in order to take sonar data on the wreck of the World War I-era armored cruiser USS San Diego (ACR 6), Sept. 11. Members from the Naval History and Heritage Command, Naval Surface Warfare Center Carderock Division, the University of Delaware, the Office of Naval Intelligence, and a USNA midshipman started surveying the shipwreck to gain scientific insight, historical clarity, and in preparation for the 100th commemoration of the vessel’s sinking. The project started with a side-scan sonar and bathometric survey. San Diego was believed to have been sunk off the coast of Long Island in 1918 by a German submarine. U.S. Navy photo by Mass Communication Specialist 1st Class Eric Lockwood/Released

“The legacy of the incident is that six men lost their lives on July 18, 1918,” said Catsambis. “With this project, we had an opportunity to set the story straight and by doing so, honor their memory and also validate the fact that the men onboard did everything right in the lead up to the attack as well as in the response. The fact that we lost six men out of upwards of 1,100 is a testament to how well they responded to the attack.”

In addition to Catsambis, the panel participants included Ken Nahshon, Ph.D., of the Naval Surface Warfare Center Carderock Division in Bethesda, Md., and Arthur Trembanis, Ph.D. from the University of Delaware in Newark, Del.

 Retired Rear Admiral Samuel Cox, Director, Naval History and Heritage Command, speaks to Sailors aboard the USNS Grasp (T-ARS-51) during a wreath-laying ceremony to commemorate the 100th anniversary of the sinking of the USS San Diego (ACR 6). Believed to be caused by a German mine or torpedo, the armored cruiser sank in 28 minutes with the loss of six lives. The ceremony was organized by the Naval History and Heritage Command, which is responsible for the preservation, analysis, and dissemination of U.S. Naval history and heritage. U.S. Navy photo by Photo by Christopher Lange/Released

Retired Rear Admiral Samuel Cox, Director, Naval History and Heritage Command, speaks to Sailors aboard the USNS Grasp (T-ARS-51) during a wreath-laying ceremony to commemorate the 100th anniversary of the sinking of the USS San Diego (ACR 6). Believed to be caused by a German mine or torpedo, the armored cruiser sank in 28 minutes with the loss of six lives. The ceremony was organized by the Naval History and Heritage Command, which is responsible for the preservation, analysis, and dissemination of U.S. Naval history and heritage. U.S. Navy photo by Photo by Christopher Lange/Released

During the presentation, the scientists detailed how each of their teams used historical analysis, archaeological research, site investigation, and impact and flood modeling to eliminate other possibilities that might have caused San Diego’s sinking such as sabotage, accident, or enemy torpedo.

Trembanis explained how the use of underwater robotics and remotely deployed instruments including an autonomous underwater vehicle allowed researchers to collect high resolution 3-D images of the site to support their conclusion.

 Vice Adm. Harley Hannibal Christy, photographed in June 1929. At that time, he was Commander Battleship Division. Earlier in his career, at the rank of captain, Christy took command of the armored cruiser San Diego (ACR-6) and was with her when she was sunk in July 1918. U.S. Navy Photo courtesy of Naval History and Heritage Command

Vice Adm. Harley Hannibal Christy, photographed in June 1929. At that time, he was Commander Battleship Division. Earlier in his career, at the rank of captain, Christy took command of the armored cruiser San Diego (ACR-6) and was with her when she was sunk in July 1918. U.S. Navy Photo courtesy of Naval History and Heritage Command

“The format of the 3-D modeling data makes analysis readily comparable,” said Nahshon. “Before we started this, I wasn’t familiar with the ability to do this underwater; above the water we do it all the time, but below water collecting 3-D data is a challenge. I’ve learned that the sheer amount of expertise that’s needed to interpret it is a credit to the advances of technology in sea floor mapping.”

Before taking questions, Catsambis shared why this research is important for the U.S. Navy and how learning from the past will help to prepare for the future.

 A white ceramic soap dish from the USS San Diego. The interior has a ridged bottom. “USN” is written on the side of the dish in black. There are no maker’s marks.

A white ceramic soap dish from the USS San Diego. The interior has a ridged bottom. “USN” is written on the side of the dish in black. There are no maker’s marks.

“The collection of archeological and hydrographic data establishes a baseline informing site formation processes and management of USS San Diego,” said Catsambis. “Lessons learned here are applicable to other U.S. Navy sunken military craft. This endeavor also provided real-world training opportunities for U.S. Navy divers, archaeologists, historians, modelers, naval engineers and graduate students.”

In July 1918, the 15,000-ton armored cruiser San Diego sank off Long Island, New York, losing six sailors from a crew of 1,100. German submarines had mined the coast, implicating a mine. But the ship’s captain was perplexed that the explosion occurred aft of the ship’s widest point which gave rise to the notion the explosion might have been caused by a torpedo even though no submarine or torpedo trail had been spotted.

Later theories suggested a coal bunker explosion or sabotage, but the source of the explosion remained a mystery.

 A M1892 bugle from the USS San Diego (Armored Cruiser No. 6) stamped with “M. SLATER NEW YORK” on the bell. Moses Slater manufactured instruments from 1865-1920. This bugle dates between 1901 and 1918. The M1892 became the standard issue bugle of the military following WWI and is still in use today by the military as well as the Boy Scouts of America.

A M1892 bugle from the USS San Diego (Armored Cruiser No. 6) stamped with “M. SLATER NEW YORK” on the bell. Moses Slater manufactured instruments from 1865-1920. This bugle dates between 1901 and 1918. The M1892 became the standard issue bugle of the military following WWI and is still in use today by the military as well as the Boy Scouts of America.

To commemorate the 100th anniversary of the loss of San Diego, the only major U.S. warship sunk in World War I, a multi-partner investigative campaign dubbed the USS San Diego Project was launched in 2017; mapping the wreck, assessing the wreck’s state of preservation, modeling its sinking, and uncovering the weapon that likely sank it.

Dive training at the site occurred in August 2016, and June 2017, with the site investigation commencing September 2017, followed by the commemoration and diver survey July 2018. A major goal of the project is to raise awareness of the importance of preserving the wreck site into the future.

 This steam valve was recovered from the San Diego. In the middle is the number “2” with the word “Patented” below followed by an etching of a flag pole and flag. Inside the flag are the letters “200 / Excelesior” with a date “Dec. 4 94” below. On the other side, not seen in the picture, are the words “Made By The Kelly & Jones Co” with a unique symbol in the middle.

This steam valve was recovered from the San Diego. In the middle is the number “2” with the word “Patented” below followed by an etching of a flag pole and flag. Inside the flag are the letters “200 / Excelesior” with a date “Dec. 4 94” below. On the other side, not seen in the picture, are the words “Made By The Kelly & Jones Co” with a unique symbol in the middle.

 This padlock was recovered from WWI-era armored cruiser, USS San Diego. The obverse side has “USN” cast into it and the reverse side not shown are cast the letters “ILCO.”

This padlock was recovered from WWI-era armored cruiser, USS San Diego. The obverse side has “USN” cast into it and the reverse side not shown are cast the letters “ILCO.”

 A USMC Marmeluke Officer’s Sword from WWI-era ship USS San Diego. This particular type of sword, Marmeluke, was adopted by the United States Marine Corps in the 19th century and usually carried as a dress sword by officers. Accession no. 2010-75-17

A USMC Marmeluke Officer’s Sword from WWI-era ship USS San Diego. This particular type of sword, Marmeluke, was adopted by the United States Marine Corps in the 19th century and usually carried as a dress sword by officers. Accession no. 2010-75-17

AGU is dedicated to the furtherance of the Earth and space sciences, and to communicating science’s ability to benefit humanity. AGU seeks to achieve these goals through publishing scientific journals and other technical publications, sponsoring scientific meetings, supporting education and outreach programs designed to increase public understanding of and support for science, and a variety of other activities.

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The Naval History and Heritage Command, located at the Washington Navy Yard, is responsible for the preservation, analysis, and dissemination of U.S. naval history and heritage. It provides the knowledge foundation for the Navy by maintaining historically relevant resources and products that reflect the Navy’s unique and enduring contributions through our nation’s history, and supports the fleet by assisting with and delivering professional research, analysis, and interpretive services. NHHC is composed of many activities including the Navy Department Library, the Navy Operational Archives, the Navy art and artifact collections, underwater archeology, Navy histories, nine museums, USS Constitution repair facility and the historic ship Nautilus.

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