Special Feature

Special Feature: US Defensive Grenades in World War I

American troops advance near Chateau Thierry, Jul-1918. Painting by Francois Flameng.

US Defensive Grenades in World War I was contributed by Glenn Hyatt

Follow this link to visit Glenn's web site: Fredericksburg Memorial Military Museum

    Mr. Hyatt's historic involvements include:
  • Company of Military Historians
  • USMC Air Ground Museum, (Quantico) Vol. Restorations Staff
  • Past Pres. Fredericksburg Civil War Round Table
  • Historian VFW Post 3103 & American Legion Post 55

US Defensive Grenades in World War I

The advances of technology had a major impact on the weapons deployed in the Great World War of 1914 - 1918. It saw the first development and applications of weapons in aviation, under sea submarines and chemical warfare. This War for Humanity also saw the first widespread deployment machine guns, barbed wire and the introduction of the lumbering armored tank. Each of these innovations, in that first of the "modern" wars, are relatively well known. However, a lesser known advance in personal weaponry for the soldier in the field was in the evolution of the Hand Grenade.

The small hand held launched "bomb" has been used in warfare for nearly as long as gunpowder had been used. The initial applications consisted of some sort of container, filled with a explosive composition, which when thrown among the enemy would detonate with (hopefully) a catastrophic effect. In our own Civil War there were several of these infernal machines deployed in the field. With the exception of the patented Ketchum Grenade grenades were most commonly adaptations of a cannon ball. Some detonated by burning a time delay fuse, others relied upon impact to postpone the detonation of the bomb until it had been delivered to the target. These primitive grenades found use on both the land and the sea with limited effect.

Until 1914 both the French and Germans used and iron ball grenade about the same size as a common 6lb cannon ball. Friction primed and sealed to protect it from the weather, they had a timed burn delay fuse which activated the charge of mostly black powder to rupture the cast iron shell. Often grenades were covered with warty lumps, nasty looking but relatively ineffective. This was the basic "state of the art" at the outbreak of hostilities in 1914

The French continued to issued the M 1870ís grenade, a smooth iron ball, with a wooden plug containing the friction fuse. The primer was attached to a tether which the soldier held when throwing to ensure it was clear win the primer was pulled. They also issued a series of pipe bombs attached to wooden paddles, known as racquet grenades. The British Tommy had a variety of contraptions available, both complex and as simple as using empty jam tins, filled with explosives and nails, with a match lit fuse. The Germans issued a iron ball grenade with scores or lumps on it. It used a brass time delay fuse activated by a wire pull friction primer. None of these were effective or reliable enough in the trench environment.

As the battle lines became fixed and the armies faced off in a stalemate often within yards of each other, the pressure for improved hand grenades grew. The Grenade was the ideal weapon for the close up, confined combat conditions of the trench. It was extremely effective for cleaning out a dugout, silencing a machine gun nest, or repelling an enemy assault when it was slowed by a wire entanglement. The period of 1914-1916 saw dozens of innovations on both sides of the front in attempt to gain the advantage.

Although there were specialty grenades, including gas and incendiary, the primary developmental effort was along two lines, defensive and offensive in nature. Offensive grenades were used in the open as well as in the assault. The propose was to limit the exposure of the Grenadier to the danger of the shell fragments. The effect was a large concussion with fragmentation limited to 8 to 10 yards beyond the busting point.

The defensive grenade on the other hand was designed to project fragments up to 100 yards from the point of explosion. The European armies put a tremendous effort to develop reliable fuses and effective fragmentation patterns.

The delay of the US entry into the war left Uncle Samís doughboys drastically behind the curve when it came to Trench Warfare tactics as well as the required material. Since the grenade was a critical tool for the trench soldier American Armies rushed to fill the gap.


A 1917 Trench Warfare training manual, by Maj. J. A Moss, relates the operation and application of the hand grenade in accordance with Ordinance Department Pamphlet #1741. The grenade illustrated as being of "US" type was only an iron cylinder, lightly scored in a checkered pattern to improve its fragmentation capability. It was fused with a rather complex impact system actuated by a fulminate primer on one end. To ensure it landed correctly and set off the bomb, the grenade included a rope tail. This tail, like a kite, streamed behind the bomb when it was thrown forcing it to land on the end and initiate the percussion device. It was fine for a dry hard field encountered on the range but inadequate in the confines of the mud filled trenches of the Western Front. Deployment of US troops with this type of device would have put them at a serious disadvantage by 1917.

In Europe the warring parties had developed weather proof, timed delay, bombs, packed with high explosive, equipped with carefully designed safety devices. Safety had always been a problem and a loose grenade in your own ranks could be as effective as a well placed enemy shell. When these new bombs ruptured they had tremendous kill ranges as the slivers of shrapnel sliced through the ranks. Even though there had been great advances the science was still rapidly developing.


US authorities, not to be out done by the allied counterparts, launched on a campaign to develop their own design. The new US design was developed by the US Army, Trench Warfare Section. In truly a mad rush, the design and drawings were completed by August of 1917. The first contract immediately followed for 5000 of the new grenades. In the weeks that followed contracts to several other manufactures were let to build a total of 68,000,000 fully assembled and loaded grenades for delivery overseas to the US troops. The grenade effort got underway with all the enthusiasm associated with the war fever of the day and full production was reached in 90 to 120 days by nearly all the companies. (Consider the task, since this included tooling and material procurement).

The entire effort came to a screeching halt in April of 1918 when a cable from the AEF condemned the new defensive grenade. The problem was that it had been designed too safe. With the zeal to protect our soldiers the fuse (Bouchon Assembly) was so complex, it took five movements for the soldier to arm the bomb. Far too complicated for a soldier in the heat of battle. Numerous incidents were recorded where bombs were hurled without completing the arming sequence. This allowed the enemy pick up the grenade, complete the arming and send it back to its origin with disastrous results.

As production came to a sudden halt there were on hand 15,000,000 rough castings, 3,500,000 assembled but empty and 1,000,000 grenades ready for shipment, now fit only for salvage. In July, just as the AEF moved into the first serious "All American" campaigns, grenade production was Zero.

In an unprecedented effort by the contractors, the redesign of the fuse was completed on paper by Aug.1, 1918. Although applying the same zeal to re-tooling enabled the phenomenal war time production figure of 17,447,245 completed grenades by Nov. 11, 1918 the US grenade was not available for the final campaigns of the Great War.

So what did we do for grenades? With the snafu at home we relied on our allies to supply our doughboys. But specifically, which grenade(s) did the US W.W.I soldier use in the great campaigns of 1918?

Americans serving with divisions in the British sectors were no doubt issued the British Mills Bomb. This was due to the convenience of using the British supply lines and the relatively low number of US troops serving under the British Command. However, the bulk of the American units were in sectors which had the benefit of the independent US supply organizations.


The French F1 was similar in appearance to the failed US grenade. It has a hollow cast iron body, heavily grooved in a familiar quilted "pineapple" pattern to enhance fragmentation. Although initially deployed to French forces in 1915 with a match primer it was soon replaced with a weather proof strike primer. This system required the soldier to strike a blow to the cap of the grenade after removing a safety cover to initiate the burn time fuse. Better than a match lit fuze, it still had to be thrown once the striker has been activated. The quest for a better fuze continued so that by 1917 there were a dozen or so contraptions developed as fuses for the French F1 Defensive Grenade. They included tumblers, pins, strikers, slow burn matches, each inventor claiming superiority.

The fuse that was favored seems to be the 1917 automatic (Billant) fuse system. It was a cast white metal fuse screwed into the head of the casing secured with a safety pin and lever. When the pin was pulled and the lever released a plunger was withdrawn allowing two hammers to fall and initiate the primer. This began a 5 second time delay burn within the fuse. When the burn completed it set off a detonator and subsequently the explosive, rupturing the case into fragments. It was, weather proof, with a couple of simple safety features built in.


I have personally conducted extensive field surveys of a variety of US positions at St. Mihiel and the Argonne battle areas over the past seven years. I feel it is safe to say the F1 with the 1917 automatic fuse was the grenade of the Doughboy. The prevalence of the F1 and its parts in both fragmentation form as well as abandoned live ordinance supports this theory. (Note: a hazard when visiting off the road WWI battlefields is the large amount of unexploded ammunition still laying around ...EVERYWHERE!)

This design was so successful that its principals were incorporated into the system that was used to replace the faulty US defensive grenade. The redesign of the US grenade incorporated the safety lever secured by a ring safety pin. The primary difference was replacing the plunger with a spring loaded hammer that directly contacted the primer to begin the time delay burn.

With the success of the new fuze the existing US castings manufactured for WWI were used in the field and deactivated for training purposes. A new US body was developed similar to the F1 but with less dramatic checking for fragmentation to reduce weight. This design was used by US forces throughout this century and is still found incorporated in many of our grenades today.


Trench Warfare, training manual, by Maj. J. A Moss, 1917
Ordinance Department Pamphlet #1741. GPO
American Munitions, 1919, GPO
Grenades Frances de la Grand Guerre (published in France)
Personal tours of the battlefields. 1987-1994
Author : Glenn Hyatt, Fredericksburg VA 01/03/1995.