A grenade is a small explosive projectile. It can be thrown by hand (hand grenade), launched by a rifle attachment, or launched by a dedicated launcher. A modern hand grenade generally consists of an explosive charge ("filler"), a detonator mechanism, an internal striker to trigger the detonator, and an arming safety secured by a transport safety. The user removes the transport safety pins before throwing, and once the grenade leaves the hand the arming safety gets released, allowing the striker to trigger a primer that ignites a fuze (sometimes called the delay element), which burns down to the detonator and explodes the main charge.
Grenades work by dispersing fragments (fragmentation grenades), shockwaves (high-explosive and stun grenades), chemical aerosols (smoke, gas and chemical grenades), fire (incendiary grenades), or a jet of metal (anti-tank grenades). Their outer casings, generally made of a hard synthetic material or steel, are designed to rupture and fragment on detonation, sending out numerous fragments (shards and splinters) as fast-flying projectiles. In modern grenades, a pre-formed fragmentation matrix inside the grenade is commonly used, which may be spherical, cuboid, wire, or notched wire. Most anti-personnel (AP) grenades are designed to detonate after a time delay and/or on impact.
Grenades are often spherical, cylindrical, ovoid, or truncated ovoid in shape, and of a size that fits the hand of an average-sized adult. Some grenades are mounted at the end of a handle and known as "stick grenades". The stick design provides leverage for throwing longer distances at the cost of additional weight and length, and has been considered obsolete by western countries since the Second World War and Cold War periods. A friction igniter inside the handle or on the top of the grenade head was used to initiate the fuse.
The origin of the English word grenade is disputed. Some derive it from the French word spelled exactly the same, meaning "pomegranate", while others claim it is taken more directly from the Latin granatus, meaning "filled with grain". The first use of the word for explosives comes from the August 1536 siege of Arles by the Emperor Charles V, while its first recorded use in English (as granades) dates from 1591.
Rudimentary incendiary grenades appeared in the Byzantine Empire, not long after the reign of Leo III (717–741). The Byzantine army learned that Greek fire, a Byzantine invention of the previous century, could not only be thrown by flamethrowers at the enemy but also in stone and ceramic jars. Later, glass containers were employed.
In Song China (960–1279), weapons known as 'thunder crash bombs' (震天雷) were created when soldiers packed gunpowder into ceramic or metal containers fitted with fuses. A 1044 military book, Wujing Zongyao (Compilation of Military Classics), described various gunpowder recipes in which one can find, according to Joseph Needham, the prototype of the modern hand grenade.
The shells (pào) are made of cast iron, as large as a bowl and shaped like a ball. Inside they contain half a pound of 'divine fire' (shén huǒ, gunpowder). They are sent flying towards the enemy camp from an eruptor (mu pào), and when they get there a sound like a thunder-clap is heard, and flashes of light appear. If ten of these shells are fired successfully into the enemy camp, the whole place will be set ablaze...
Grenade-like devices were also known in ancient India. In a 12th-century Persian historiography, the Mojmal al-Tawarikh, a terracotta elephant filled with explosives set with a fuse was placed hidden in the van and exploded as the invading army approached.
A type of grenade called the 'flying impact thunder crash bomb' (飛擊震天雷) was developed in the late 16th century and first used in September 1, 1592 by the Joseon Dynasty during the Japanese invasions of Korea. The grenade was 20 centimetres (7.9 in) in diameter, weighed 10 kilograms (22 lb), and had a cast iron shell. It contained iron pellets, and an adjustable fuse. The grenade was used with a dedicated grenade launcher called a 'wangu' (碗口). It was used in both the besieging and defense of fortifications, to great effect.
There is a documented precedent for the use of hand grenades by Catalan troops. At the very least, they were already utilized during the siege of Bonifacio in 1420. Another specific historical instance occurred in 1433: The fleet of Alfonso the Magnanimous (Alfons el Magnànim), which set sail for Sicily, loaded 200,000 units of primitive "magranes de coure" (copper pomegranates in the Italian language of the time) in Barcelona. The historical account describes them as follows:"...It also carried 200,000 copper pomegranates filled with gunpowder, and when they set fire to them they made a great noise, and, as the pieces shattered, they did so much damage that they knocked to the ground anyone they touched..." — Melcior Miralles: Chronicle and Diary of the Chaplain of Alfonso the Magnanimous. The key innovation here was the fragmentation effect. Older grenades relied mostly on fire to burn the enemy. The Catalan copper grenades were designed to explode and spray metal shrapnel, making them a true ancestor of the modern fragmentation grenade. Moreover the quantity indicates they were a standard issue munition, not just an experimental prototype.
The first cast-iron bombshells and grenades appeared in Europe in 1467, where their initial role was with the besieging and defense of castles and fortifications. A hoard of several hundred ceramic hand grenades was discovered during construction in front of a bastion of the Bavarian city of Ingolstadt, Germany, dated to the 17th century. Many of the grenades retained their original black powder loads and igniters. The grenades were most likely intentionally dumped in the moat of the bastion prior to 1723.
By the mid-17th century, infantry known as "grenadiers" began to emerge in the armies of Europe, who specialized in shock and close quarters combat, mostly with the usage of grenades and fierce melee combat. In 1643, it is possible that grenados were thrown amongst the Welsh at Holt Bridge during the English Civil War. The word grenade was also used during the events surrounding the Glorious Revolution in 1688, where cricket ball-sized (8.81 to 9 in (224 to 229 mm) in circumference) iron spheres packed with gunpowder and fitted with slow-burning wicks were first used against the Jacobites in the battles of Killiecrankie and Glen Shiel. These grenades were not very effective owing both to the unreliability of their fuse and the inconsistent times to detonation as a result, saw little use. Grenades were also used during the Golden Age of Piracy, especially during boarding actions; pirate Captain Thompson used "vast numbers of powder flasks, grenade shells, and stinkpots" to defeat two pirate-hunters sent by the Governor of Jamaica in 1721. By the 18th century, the popularity of hand grenades was declining
The fledgling American Navy used hand grenades as Captain Tyringham Howe reported one thrown from the top mast of a ship intercepting HMS Glasgow, 6 April 1776 in what is known as the Battle of Block Island.
Mexican forces used grenades in the Battle of the Alamo.
Improvised grenades were increasingly used from the mid-19th century, the confines of trenches enhancing the effect of small explosive devices. In a letter to his sister, Colonel Hugh Robert Hibbert described an improvised grenade that was employed by British troops during the Crimean War (1854–1856): Hand grenades were used by French and Russian forces during the Siege of Sebastopol.
We have a new invention to annoy our friends in their pits. It consists in filling empty soda water bottles full of powder, old twisted nails and any other sharp or cutting thing we can find at the time, sticking a bit of tow in for a fuse then lighting it and throwing it quickly into our neighbors' pit where it bursts, to their great annoyance. You may imagine their rage at seeing a soda water bottle come tumbling into a hole full of men with a little fuse burning away as proud as a real shell exploding and burying itself into soft parts of the flesh.