Portrait of a Group of Communard Soldiers Posing With Two Cannon at a Barricade During the Paris Commune (1871)

 Portrait of a group of Communard soldiers posing with two cannon at a barricade during the Paris Commune in Paris, France, 1871. Cabinet card-sized albumen print taken by photographer Bruno Braquehais.

Source: J. Paul Getty Museum.

A French Soldier Posing at the Entrance of an Aid Station in a Trench During World War 1

A French soldier posing at the entrance of an aid station in a trench during World War 1. By Raoul Berthelé.

Source: City Archives of Toulouse.

Union Soldiers Posing on Sandbag Fortifications and With Parrott Rifles in Battery Stevens on Morris Island Near Charleston, South Carolina (1863)

Union soldiers posing on sandbag fortifications and with Parrott rifles in Battery Stevens on Morris Island, South Carolina, 1863. Battle smoke from nearby artillery fire is possibly visible in the background. By Haas and Peale.

Source: Library of Congress.

An American Soldier Firing a Chauchat Light Machine Gun From Behind a Barricade Made of Sandbags and Ammunition Boxes During World War 1 (1910's)

An American soldier firing a Chauchat light machine gun from behind a barricade made of sandbags and ammunition boxes during World War 1.

A British Soldier Posing With a Rifle Grenade in a Trench Somewhere in the Balkans During World War 1

A British soldier posing with a rifle grenade in a trench somewhere in the Balkans during World War 1. Published by the Keystone View Company. Animated stereoview.

Source.

Entrenched Boer Artillery and Soldiers Posing For a Photograph During the Siege of Ladysmith in Natal, South Africa, During the Second Boer War (1899)

Entrenched Boer artillery and soldiers posing for a photograph during the Siege of Ladysmith in Natal, South Africa, during the Second Boer War, c. 1899.

Source.

Canadian Soldiers Posing in a Reserve Trench on the Western Front During World War 1

Canadian soldiers posing in a reserve trench on the Western Front during World War 1.

Source.

Two Scenes of Union Soldiers Posing on Earthworks Near Atlanta, Georgia (1864)

Two scenes of Union soldiers posing on earthworks near Atlanta, Georgia, July 1864. By George Barnard. Animated stereoscopic photographs.

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Source 2.

Time-Lapse View of Union Soldiers Posing With the Wreckage of the Swamp Angel on Morris Island, South Carolina (1863)

Close-up view of the barrel of the 8-inch Parrot gun and the Union soldiers playing cards,

Time-lapse view of Union soldiers posing with the wreckage of the Swamp Angel, a gun emplacement for an 8-inch Parrot gun which was built in swampland on Morris Island, 1863. It fired incendiary shells into downtown Charleston, a distant 4.5 miles away, until it burst during its 36th shot on August 23, 1863. Two of the soldiers near the barrel of the Parrot gun are playing a card game. By Haas and Peale.

Source 1.
Source 2.
More information.

Two Views of an Unidentified Man Posing in Front of a Bombproof in Fort Sedgwick Which Was Built by Union Troops During the Siege of Petersburg Near Petersburg, Virginia (1865)

First view of the man posing in front of the bombproof in the foreground on the left.

View of the background on the right.

Second view of the man posing in front of the bombproof.

Two views of an unidentified man posing in front of a bombproof in Fort Sedgwick which was built by Union troops during the Siege of Petersburg near Petersburg, Virginia, 1865. A group of Union soldiers are seen posing in the background to the right of the first stereoscopic view. Animated stereoscopic photographs.

Source 1.
Source 2.

Three Men Posing With Two Mortars in the Trapier Mortar Battery on Morris Island Shortly After the Surrender of the Nearby Fort Sumter by Union Forces in Charleston Harbor (1861)

Three men posing with two mortars in the Trapier Mortar Battery on Morris Island shortly after the surrender of the nearby Fort Sumter by Union forces in Charleston Harbor, 1861. The battery fired its mortars at Fort Sumter in the bombardment leading to its surrender. The darkroom used by the photographers to develop this photograph is visible behind the mortar in the background. By Osborn and Durbec. From The Blue and Gray in Black and White: A History of Civil War Photography.

Irish Soldiers of the Royal Munster Fusiliers Posing as if Fighting From Behind a Redoubt at Honey Nest Kloof, South Africa (1900)

Irish soldiers of the Royal Munster Fusiliers posing as if fighting Boer forces from behind a redoubt at Honey Nest Kloof, South Africa, c. 1900.

Source.

A Japanese Mine Exploding Under the Defenses of a Russian-held Fort on East Kikwan Hill During the Siege of Port Arthur (1904)

Photograph of a Japanese mine exploding under the defenses of a Russian-held fort on East Kikwan Hill during the Siege of Port Arthur, 1904. Probably the first photograph of a mine explosion during a conflict. The second photograph is of Japanese infantry assaulting the same Russian fort and was probably taken soon after the mine exploded.

MFA version of first image.

Source of second image.

Russian Officers Watching a Japanese Assault on a Russian Fort During the Siege of Port Arthur

Russian officers watching a Japanese assault on a Russian fort during the Siege of Port Arthur, 1904.

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British Soldiers During Training

British soldiers during training. The soldier with the bayonet to his ear is demonstrating a technique used to detect enemy movements by listening to their ground vibrations. Animated stereoview.

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Japanese Troops Killed in an Assault on a Russian Fort During the Siege of Port Arthur (1904)

Russian soldiers posing with Japanese troops killed in an assault on a Russian fort during the Siege of Port Arthur, 1904. Animated stereoview.

Source.

Two French Soldiers in a Trench

Two French soldiers observing the area in front of their trench. Animated stereoview.

Animated Stereoview of British Soldiers in a Trench Demonstrate Keeping Watch Over No Man's Land With a Mirror (1910s)

British soldiers keeping watch over the top of their trench with a mirror. Published by Keystone View Company.

Source: New York State Military Museum.