Lattice masts, or cage masts, are a type of observation mast common on major warships in the early 20th century. They were used most prominently on American dreadnought

Dreadnought

The dreadnought was the predominant type of 20th-century battleship. The first of the kind, the Royal Navy's had such an impact when launched in 1906 that similar battleships built after her were referred to as "dreadnoughts", and earlier battleships became known as pre-dreadnoughts...

 battleship

Battleship

A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...

s and armored cruiser

Armored cruiser

The armored cruiser was a type of warship of the late 19th and early 20th centuries. Like other types of cruiser, the armored cruiser was a long-range, independent warship, capable of defeating any ship apart from a battleship, and fast enough to outrun any battleships it encountered.The first...

s of the World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 era. Observation posts were mounted on the masts and used to direct the fire of the warships' guns. The purpose of the lattice structure was to make the posts less vulnerable to shells from enemy ships, and to better absorb the recoil shock associated with firing main guns, isolating the delicate fire control equipment (rangefinders, etc) mounted on the mast tops. The masts are a type of hyperboloid structure

Hyperboloid structure

Hyperboloid structures are architectural structures designed with hyperboloid geometry. Often these are tall structures such as towers where the hyperboloid geometry's structural strength is used to support an object high off the ground, but hyperboloid geometry is also often used for decorative...

, whose weight-saving design was first used by the Russian engineer Vladimir Shukhov

Vladimir Shukhov

Vladimir Grigoryevich Shukhov , was a Russian engineer-polymath, scientist and architect renowned for his pioneering works on new methods of analysis for structural engineering that led to breakthroughs in industrial design of world's first hyperboloid structures, lattice shell structures, tensile...

.

Use in the US Navy

The South Carolina class battleships

South Carolina class battleship

The United States Navy's South Carolina class consisted of two battleships: and , both of which were launched in 1908. These were among the first warships built with armament organized on the "all-big gun" and the first American battleships of the type...

 were the first class of American battleships to feature lattice masts, which were to become a standard fixture on all American battleships, and many cruiser classes. All American battleships, up to the Colorado class

Colorado class battleship

The Colorado class battleships was a group of four battleships built by the United States Navy after World War I. However, only three of the ships were completed: , , and . The fourth, , was over 75% completed when she was canceled under the terms of the Washington Naval Treaty in 1922...

 battleships were equipped with lattice masts, although in the 1920s–30s, the older battleships had their lattice masts replaced with more modern tripod masts. The newer Tennessee

Tennessee class battleship

The Tennessee class was a class of battleships of the United States Navy. The class comprised two ships: and the . They were modified versions of the featuring improved underwater armor for better torpedo protection and 30 degree elevation on their main batteries, as opposed to 15 degrees for...

 and Colorado

Colorado class battleship

The Colorado class battleships was a group of four battleships built by the United States Navy after World War I. However, only three of the ships were completed: , , and . The fourth, , was over 75% completed when she was canceled under the terms of the Washington Naval Treaty in 1922...

 classes retained their original lattice masts at the start of World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

.

Use in the Russian Navy

The two "Andrei Pervozvanny" class battleships

Andrei Pervozvanny class battleship

The Andrey Pervozvanny class were a pair of predreadnought battleships built in the mid-1900s for the Baltic Fleet of the Imperial Russian Navy. They were conceived by the Naval Technical Committee in 1903 as an incremental development of the Borodino class battleships with increased displacement...

 had lattice masts until they were replaced with conventional masts in the beginning of the First World War. The four "Gangut" class battleships

Gangut class battleship

The Gangut-class battleships were the first dreadnoughts begun for the Imperial Russian Navy before World War I. They had a convoluted design history involving several British companies, evolving requirements, an international design competition, and foreign protests...

 were designed with lattice masts, but constructed with conical ones.

Use in the Argentine Navy

The two Rivadavia class battleship

Rivadavia class battleship

The Rivadavia class was a two-ship group of battleships designed by the American Fore River Shipbuilding Company for the Argentine Navy...

s, the ARA Rivadavia

ARA Rivadavia

ARA Rivadavia"ARA" is an acronym for Armada de la República Argentina was a battleship of the Argentine Navy. Named after the first Argentine president, Bernardino Rivadavia, she was the lead ship of her class and the third dreadnought built during the South American dreadnought race...

 and the ARA Moreno

ARA Moreno

ARA Moreno was a dreadnought battleship designed by the American Fore River Shipbuilding Company for the Argentine Navy...

had lattice masts. They were the only dreadnought-type battleships built by for export by the USA.