The USS Idaho (BB-42), a New Mexico-class battleship commissioned in 1919, played a crucial role in the United States Navy’s operations throughout its nearly three decades of service, especially during World War II.

It was a technological marvel of its time, equipped with twelve 14-inch guns and advanced armor, showcasing the pinnacle of early 20th-century naval engineering and firepower.

After providing significant support in key battles across the Pacific, including the Aleutian Islands Campaign and the Battle of Okinawa, the Idaho was decommissioned in 1946.


Construction of the USS Idaho

The USS Idaho (BB-42), a New Mexico-class battleship, stands as a notable symbol of early 20th-century American naval engineering and military might. Its construction began amidst a period of intense naval armament, driven by global competition and the shifting dynamics of maritime power.

The keel of the USS Idaho was laid down on April 24, 1915, at the New York Shipbuilding Corporation in Camden, New Jersey, marking the commencement of a project that would contribute significantly to the United States’ naval capabilities.

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Designed to be a formidable presence on the high seas, the Idaho was equipped with advanced technology and weaponry for its time. It was launched on June 30, 1917, a time when the world was engulfed in the First World War, although the ship would not see action in this conflict.

The Idaho was officially commissioned into the United States Navy on March 24, 1919, under the command of Captain Carl T. Vogelgesang. This timing meant that the USS Idaho missed participation in World War I but was poised to play a pivotal role in the U.S. Navy’s operations during the interwar period and beyond, into World War II.

USS Idaho in Hampton Roads, June 1927.

The battleship’s design reflected the culmination of early 20th-century naval architecture and armament philosophy. It measured over 600 feet in length and had a beam exceeding 97 feet, with a displacement of over 32,000 tons. Its propulsion system, comprising geared turbines and 12 boilers, enabled the vessel to reach speeds of up to 21 knots—a formidable pace for such a large ship at the time.

Armament was a critical aspect of the Idaho’s design, with a main battery consisting of twelve 14-inch/50 caliber guns arranged in four triple turrets. This powerful armament allowed the Idaho to engage enemy ships and shore positions with devastating effect. Additionally, the ship boasted a secondary battery of 14 5-inch/51 caliber guns for defense against smaller vessels and aircraft, along with an array of anti-aircraft guns that were updated throughout its service life.

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The Idaho’s armor was equally impressive, featuring a belt of up to 13.5 inches of steel in critical areas to protect against enemy fire. The ship’s deck, turrets, and conning tower were also heavily armored, ensuring the vessel’s resilience in battle.

Pre-World War II Service

In the years following its commissioning, the USS Idaho served primarily with the Pacific Fleet, a strategic positioning that reflected the United States’ growing interest in Asia and the Pacific region amidst rising tensions with Japan. The battleship’s early assignments included routine patrols, training exercises, and goodwill visits to foreign ports.

These activities were not only vital for maintaining crew proficiency and operational readiness but also served as a form of naval diplomacy, demonstrating the United States’ commitment to peace and stability in international waters.

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A significant aspect of the Idaho’s pre-World War II service was its participation in fleet problems, which were large-scale naval exercises designed to test tactics, strategy, and ship performance under simulated combat conditions. These exercises, held annually, allowed the Navy to experiment with new technologies and operational concepts, including carrier aviation and amphibious warfare, which would become central to naval strategy in World War II.

The USS Idaho played a crucial role in these exercises, often acting as both a target and a platform for testing the effectiveness of various naval guns, torpedoes, and defensive maneuvers against aerial and surface threats.

Recognizing the rapid advancements in naval technology and the changing nature of naval warfare, the U.S. Navy initiated a series of modernization efforts in the 1920s and 1930s to ensure that its fleet, including the Idaho, remained competitive on the world stage. For the Idaho, this meant extensive refits and upgrades designed to enhance its combat effectiveness.

USS Idaho following her refit, 1934.

Between 1929 and 1931, the Idaho underwent significant modernization work, which included improvements to its propulsion system, allowing for greater speed and efficiency; the installation of new fire-control systems to enhance the accuracy of its guns; and the addition of anti-aircraft weaponry to counter the growing threat of aerial attacks. The battleship’s armor protection was also augmented, particularly around vital areas such as the magazines and engine rooms, to improve survivability in combat.

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As the 1930s drew to a close and the world moved inexorably towards another global conflict, the USS Idaho’s activities shifted more towards preparations for potential hostilities. Training exercises became more focused on combat readiness, and the ship’s crew was drilled extensively in gunnery, damage control, and anti-aircraft defense. The Idaho, along with the rest of the U.S. Navy, was being readied for a war that many saw as inevitable.

USS Idaho During WWII

One of the USS Idaho’s first major actions in World War II was its participation in the Aleutian Islands Campaign in 1943. This campaign was part of a broader strategy to expel Japanese forces from occupied territories on the Alaskan islands of Attu and Kiska, which were seized following the attack on Pearl Harbor. The occupation posed a direct threat to the North American mainland and served as a diversionary tactic by Japan to dilute American military efforts in the Pacific.

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The Idaho provided crucial bombardment support during the operations to retake these islands, using its powerful main guns to destroy enemy fortifications and support ground troops. The campaign underscored the strategic importance of the Aleutians and highlighted the Idaho’s versatility in adapting to combat operations in harsh, inhospitable environments.

USS Idaho bombarding Iwo Jima, February 1945.

As American forces pivoted towards the Central Pacific, the USS Idaho was at the forefront of the island-hopping strategy aimed at capturing key Japanese-held islands, thereby inching closer to Japan itself. The battleship’s heavy guns supported amphibious landings on the Gilbert and Marshall Islands, softening enemy defenses and providing cover for the Marines and soldiers who stormed the beaches. The Idaho’s role was not limited to initial assaults; it also provided sustained fire support for ground operations, ensuring American troops could advance against entrenched Japanese positions.

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In the Marianas campaign, particularly during the Battle for Saipan in 1944, the Idaho again demonstrated its importance in amphibious warfare. Its bombardment facilitated the capture of strategic islands, crucial for establishing airfields from which long-range bombers could strike the Japanese mainland.

The USS Idaho also participated in the liberation of the Philippines, a series of battles that were critical to cutting off Japan from its occupied territories in Southeast Asia and the Pacific. The Idaho’s main guns supported landings on Leyte and Luzon, contributing to the overwhelming firepower that eventually secured these islands from Japanese control. The battleship’s presence in the Philippine Sea, including participation in the Battle of Leyte Gulf, underscored its role in achieving American naval supremacy in the Pacific.

Idaho pictured from USS West Virginia, firing her 14 inch guns on shore positions in Okinawa.

Perhaps the most grueling test of the Idaho’s capabilities came with the Battle of Okinawa in 1945. The battleship provided intensive fire support for one of the largest amphibious assaults of the Pacific War. The Idaho’s guns bombarded Okinawa for days, destroying enemy fortifications and providing cover for advancing troops. The battle was a testament to the brutal nature of the Pacific War, with the Idaho facing not only traditional naval and ground threats but also kamikaze attacks, against which it successfully defended.

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Throughout World War II, the USS Idaho’s service was emblematic of the changing nature of naval warfare and the enduring value of battleships in providing fire support for amphibious operations. Despite the rise of air power and the carrier as the centerpiece of naval strategy, the Idaho and its sister ships proved indispensable in their roles, supporting ground forces and engaging enemy shore installations.


Following its distinguished service in World War II, the USS Idaho (BB-42) transitioned into the post-war era.

The end of World War II saw a profound transformation in naval warfare, with the advent of nuclear weapons and the rise of air power fundamentally altering the strategic value of battleships.

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The USS Idaho, like many of its contemporaries, found itself an anachronism in this new era. After participating in Operation Magic Carpet, the massive effort to repatriate U.S. troops from overseas, the Idaho was decommissioned on July 3, 1946.

Its decommissioning was a quiet end to a storied career, and in 1947, the battleship was sold for scrap, closing the chapter on a vessel that had served the United States Navy for nearly three decades.

Her Sister Ships

The USS Idaho (BB-42) was the third and final ship of the New Mexico-class battleships, a trio of vessels that served as the backbone of the U.S. Navy’s battleship fleet in the early to mid-20th century. The Idaho’s sister ships were the USS New Mexico (BB-40) and the USS Mississippi (BB-41), both of which shared similar design specifications and operational histories.

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All three New Mexico-class battleships shared core design elements, including their main armament of twelve 14-inch/50 caliber guns, robust armor plating, and the capability to reach speeds of up to 21 knots. They underwent significant modernizations throughout their careers, particularly in anti-aircraft armament and fire control systems, to keep pace with the evolving demands of naval warfare.

The sister ships of the USS Idaho collectively participated in both World Wars, playing key roles in the Pacific Theater of World War II by providing naval gunfire support for amphibious operations and engaging in surface combat operations.

USS New Mexico (BB-40)

Commissioned: May 20, 1918

The USS New Mexico, as the lead ship of her class, introduced several technological advancements over previous battleship designs, including turbo-electric propulsion, which contributed to greater efficiency and operational flexibility. Throughout her career, the New Mexico was involved in various peacetime operations, training exercises, and diplomatic missions during the interwar period.

During World War II, she played a significant role in the Pacific Theater, participating in the liberation of the Philippines, the Battle of Okinawa, and bombarding Japanese positions in the Kuril Islands. After the war, the New Mexico was decommissioned on July 19, 1946, and subsequently scrapped.

USS New Mexico off New York City, 1934.

USS Mississippi (BB-41)

Commissioned: December 18, 1917

The USS Mississippi had a distinguished career that mirrored the shifts in naval strategy and technology of the 20th century. Before World War II, she served primarily in the Pacific Fleet, engaging in training and fleet exercises while undergoing several modernizations to enhance her combat capabilities.

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In World War II, Mississippi supported numerous amphibious assaults, including the invasions of the Gilbert and Marshall Islands, the Marianas, and the Philippines, as well as providing naval gunfire support during the Battle of Okinawa.

Unique among her sisters, after World War II, the Mississippi served as a gunnery training ship before being repurposed as a test ship for missile technology in the 1950s. She was eventually decommissioned on September 17, 1956, and scrapped.