Mortars, Mortar-bombs and Hand-grenades

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This article was originally written (and translated into Dutch) for a pamphlet describing archaeological finds from the Siege of Ostend (1601-4), which the Fairfax Battalia helped to re-enact a few years ago: hence the many Flemish references. A further version was republished, with added English Civil War references, when Fairfax was preparing to re-enact the Siege of Newark in 2006. The current version has been further augmented (2011).

MORTARS

Unlike cannon which shot their balls in a direct line, mortars were short-barrelled, wide-mouthed guns, which shot their projectiles at a high angle so that they dropped onto the target. They were thus used against walled fortifications (like Ostend in 1601-4 and Newark in 1644-6), or against earthworks, trenches and other targets where the enemy could not be directly seen by the artillerymen.

Mortars might be of cast bronze, or sometimes of iron. The only surviving English Civil War mortar, ‘Roaring Meg’ - used at the siege of Goodrich Castle in 1645 and now once again on display there - is a fairly crude iron piece.

(Goodrich Castle - an English Heritage site - is open to the public). Mortars could fire several kinds of projectile, including solid balls of iron or stone, combustible fireballs or exploding bombs. The charge of gunpowder had to be carefully calculated according to the weight of the projectile, and packed down into the mortar with a layer of hay or other wadding and a pad of soft wood between the charge and the projectile. If any gap was left between charge and projectile, the mortar might well burst in the mortar barrel on firing - one of the many dangers which made mortars almost as hazardous to the firers as to the enemy. The weapon was (very approximately and unreliably) aimed with a quadrant, which calculated the angle at which the gun had to be inclined to drop its projectile onto a given target.

MORTARS AND MORTAR BOMBS AT THE SIEGES OF OSTEND, NEWARK, AND OTHER PLACES

Mortars are recorded in use by both sides at the Siege of Ostend. The defenders possessed at least two bronze mortars, which they used to fire on the approaching Spanish siege-works, while from the early stages of the siege the attacking Spanish frequently bombarded the town with mortars shooting solid iron and stone balls, incendiary fireballs and bombs. According to Philip Fleming’s contemporary history of the siege, it was these incendiary granaaten (or grenadoes) which caused most damage, destroying houses and killing large numbers both of soldiers and civilians.

A remarkable story from Newark demonstrates that grenadoes were also used against that town, at least during the 1644 siege. On the night of 11 March 1644, Hercules Clay, Royalist Mayor of Newark, repeatedly dreamt that his house was on fire. Twice he arose, found nothing amiss, and went back to bed. But after the third dream he hustled his family out of the house, which moments later was demolished by an exploding Parliamentarian mortar bomb. In his will he left a sum of money to finance an annual anniversary sermon to commemorate his miraculous deliverance, at which penny loaves were also distributed to the poor. This sermon is still preached.

Seventeenth century mortar bombs were hollow iron spheres, filled with gunpowder which was intended to explode on impact. An example can be seen at Helmsley Castle in Yorkshire (English Heritage), presumably dating from the 1644 siege under Sir Thomas Fairfax. Each had its own ignition fuze, set into a tapering wooden plug which sealed a hole cast in the bomb. This fuze had to be filled with an amount of gunpowder adjusted to remain burning while the bomb was in flight: it had to be lit a very short and carefully calculated time before the mortar itself was fired. When the bomb struck the ground, sparks from the fuze would drop into the gunpowder within, exploding it on the target.

That at least was the theory. But in fact 17th century mortar bombs were a highly unreliable weapon. If for instance the main charge intended to project the bomb from the mortar failed to ignite, the bomb might explode in the gun, with disastrous results. Alternatively the fuze might go out in mid-air, or be extinguished when the bomb fell into water, or fuze-down into mud - bombs were cast thicker at the bottom so that they fell fuze-up, but this did not always work.

Certainly many bombs used at Ostend are recorded as having failed to explode: three of these have been discovered during the recent excavations.

Despite their hazards for their operators, mortars were used to great effect during several English Civil War sieges. They were crucial in the siege of Goodrich Castle, 1645, and in the eventual surrender of the great Royalist fortress of Raglan Castle in 1646. At the siege of Chirk Castle, Flintshire in 1659 (when the owner, Sir Thomas Myddleton, prematurely rebelled against the Commonwealth), the mere threat of their use by an attacking force under General Lambert

prompted immediate capitulation.

THE OSTEND MORTAR BOMBS

The two larger Ostend bombs, of similar size, were sent to the British Royal Armouries at Fort Nelson for investigation and conservation, one being later cut in half for display. These are now on display at the Domein Raversijde, near Ostend.

The two very heavy bombs were initially transported by the author from Ostend to the Royal Armouries, Leeds, in his long-suffering Volvo. Having all the proper documentation, we had no trouble with customs or on the ferry. But on arrival at Leeds, a security man took one look at them before ordering the whole site to be cleared of the public. Calm was only restored when a curator pointed out that, since the bombs had (a) been buried in damp soil for over four centuries and (b) were obviously full of liquid, they were not very likely to explode.

Both these cast iron bombs were found to be filled with a black sticky residue, probably the remains of gunpowder degraded into its component parts by long immersion in water. Both had nozzles for tapering wooden fuzes, which were still in place when the bombs were excavated. One surviving fuze has a cap of lead or tin sheeting over the wooden plug, probably intended to protect the fuze and contents of the bomb from water penetration.

Both the bombs retained a single cast-in iron loop: it is possible but by no means certain that they each originally had a pair of loops. Bombs with a single loop appear usually to be of earlier date than those with two. During the loading process these loops would have had ropes threaded through them, to allow the very heavy and unwieldy bombs to be lowered slowly into the mortar, often using a simple crane.

The diameter of both bombs, measured as excavated and before the removal of rust accretions, was approximately 314mm, corresponding to 12.34 English inches (the unit of measurement in general use in Flanders and elsewhere before Napoleonic metrification). The weight of one example, after emptying, was approximately 68 kilograms, corresponding to 150 17th century pounds. These measurements make it likely that the bombs were shot from large mortars of 13 English (or 12 French) inches calibre: a relatively common type during the 17th and 18th centuries, these fired a bomb weighing around 150 pounds. ‘Roaring Meg’ at Goodrich, mentioned above, is a 13 inch mortar.

The third, smaller, mortar bomb retains the remains of its wooden fuze plug (which at 4.5 - 4.7 cms diameter corresponds to the size of the fuzes in the larger examples), and traces of at least one carrying loop. It has a diameter (including accretions) of approximately 18cms (or 7 inches) and a weight (including contents and accretions) of 18.5 - 19kgs (or just over 40 pounds). It thus appears to have been intended for one of the smaller standard 17th century mortars of just over 7 inch calibre, which shot a 40 pound projectile.

HAND-GRENADES

Hand grenades (or handt-boomen - hand bombs - as the contemporary Philip Fleming called them) operated on much the same principles as mortar bombs, but were much smaller and thrown by hand. Like their modern fragmentation counterparts, they were employed to often deadly effect during close-action assaults on fortifications. To get close enough to throw them required a great deal of bravery (or foolhardiness): grenadiers were therefore regarded as elite troops, and the cap-badges of many British regiments, including the Grenadier Guards, still feature an exploding grenade motif. Their use in great numbers by both sides is very often recorded during the Ostend Siege of 1601-4. They are also sometimes recorded during the English Civil War, as when in 1645 the Parliament forces drove off the defenders of Holt Bridge, Flintshire, by pelting them with grenadoes.

Seventeenth century hand grenades were hollow spheres filled with gunpowder, ignited by a length of the slow match (cord soaked in saltpetre) also used by musketeers to fire their guns.

Lit just before the hand grenade was thrown, the burning match was intended to drop into the sphere and ignite its contents on impact. Spherical with a short tube protruding from the top, their resemblance to pomegranates (apples of Granada) apparently gave them their name of granates or grenadoes.

Such grenades might be made of hollow iron, wood, or even (a Spanish speciality) glass. Fleming records 40 ‘…houte (wooden) handt-boomen…’ and 10 ‘…ysere (iron) hand-boomen…’ among the ammunition left behind by the defenders at the end of the Ostend siege. A single complete iron hand grenade, obviously never used, has been excavated at Ostend and is now displayed at Domein Raversijde.

Charles Kightly. 2003, revised 2006 and 2011.