Tuesday, 21 September 2010

Making an impression!

Extract of information from Wikipedia:

The Tsar Cannon is an enormous cannoncommissioned in 1586 by Russian Tsar Feodor and cast by Andrey Chokhov.
The cannon weighs 39.312 metric tonnes and has a length of 5.34 m (17.5 ft). Its bronze-cast barrel has a calibre of 890 mm (35.0 in), and an external diameter of 1,200 mm (47.2 in). The Guinness Book of Records lists it as the largest bombard by calibre.
Along with a new carriage, the 1 ton cannonballs surrounding the cannon were added in 1835 and are larger than the diameter of its barrel. According to legend, these cannonballs were manufactured in St. Petersburg, and were intended to be a humorous addition and a symbol of the friendly rivalry between Moscow and St. Petersburg. It was, in fact, designed to fire 800 kg stone grapeshot
The cannon is decorated with reliefs, including one depicting Tsar Feodor Ivanovich on a horse. The original wooden carriage was made in the early 19th century, but it was destroyed by fire in 1812 when Napoleon descended on Moscow.
This seems to be a classic case of 'mine's bigger than yours!' This was a time when an absolute ruler like the Tsar of Russia could demand whatever he wanted, and a bombard like this was more a statement of power than a viable—or even necessary—weapon of war. However, on its original wooden carriage, it could have been used in siege warfare, where its heavy stone shot would have had a powerful effect on the walls of any fortress. It is not known to have been used in any campaign, though there is apparently evidence that it was, at least, tested.
The carriage on which it is mounted now is purely decorative, rather like that of the Bhurtpore Gun in the Royal Artillery collection, now on show at the Royal School of Artillery, Larkhill. It could not be used in action without the severe risk of accident!
It is said that the cannonballs were intended as decoration for this display and even over-sized to make the point. In fact, bombards of this period were actually designed for stone shot or the so-called 'grapeshot' mentioned in the Wikipedia article (though these were not strictly grapeshot because the rocks were not bound together to look like a bunch of grapes, as iron shot were, mainly for naval use). The charge needed to drive the extra weight of full size iron shot would have risked bursting the gun.
That said, this is a magnificent example of bronze casting on a gigantic scale. It is interesting to compare it with the Dardanelles Gun of 630mm calibre, cast by the Turks over 100 years earlier for action at Constantinople in 1453. This gun is currently at Fort Nelson at Portsmouth, but was originally acquired by General Lefroy for the Royal Artillery collection.

Thursday, 27 May 2010

Siege Warfare - Part 2

One of the first actions taken by the attacking commander at a siege would be to call upon the fortress to surrender. If it did so, this usually meant a guarantee that there would be no reprisals, whereas if the fortress forced the besieging army to go through all the process of a siege, it often led to brutal scenes in the immediate aftermath of the fall.

Many fortified town and castles were besieged on more than one occasion. Lessons learned in one siege were often recorded and used next time around, sometimes decades later, more often by the attacker than the defender. During the Peninsular War, Badajoz, on the Spanish/Portuguese border, was besieged twice by the Allied force under Wellington: it was successful on the second attempt, but led to a savage attack by rioting soldiers on the unfortunate inhabitants.

The Siege of San Sebastian on the north coast of Spain was begun and then lifted in order to deal with a more pressing problem, but it was successful at the second attempt, despite the fact that the fortress was being supplied by sea. Here, too, was another unusual feature in that the battering guns were much further than usual from the citadel due to the intervening stretch of water that almost surrounded it. This demanded very high standards of accuracy from the guns.

Evidence of the standards achievable can be seen in one particularly unusual event during the Siege of San Sebastian - probably the first recorded instance of artillery firing in support over the heads of attacking troops. On this occasion the commander of the Right Attack saw that, having breached the outer walls, the attack was failing because the defenders had built a second wall facing the breach and were using it as protection from which to shoot troops scrambling over the rubble. He directed his guns at the French riflemen on top of this defensive wall and did so to such effect that their fire was neutralized. When the wall was passed, the attackers found a large number of headless bodies! This fire was at a range of over 600 metres.

It appears that much of this accuracy was due to the use of clinometers to lay the guns - possibly one clinometer taken down the line of guns by an officer, with each gun firing in turn rather than firing salvoes. This would also reduce the effect of smoke from one gun 'blinding' the layers on guns downwind and make it easier for an observer with a telescope to correct fire, since he could see individual 'strikes'. We know that the commander of the Right Attack kept a log of the action while observing during this siege.

Thursday, 15 October 2009

Siege Warfare - Part 1

For most of the period known as the Middle Ages and onwards into the 20th Century, sieges have been a recognized and regular form of warfare. Whether the defenders were in a traditional castle or walled town, or simply holding a piece of territory with strong defences, the process of attacking is known as a 'siege'. I will use the term 'fortress' throughout for the sake of keeping it simple.

In this piece, I will deal with sieges typical of the period 1600-1850, but the principles can be extended over a wider period.

Sieges were usually undertaken in the course of a campaign in another country or during a civil war, when the attacking army needed to make progress but was loth to leave a defended fortress in its rear. There was always the danger of defenders in these places sallying forth to attack the army's lines of communication. The answer was to 'lay siege' to the fortress and capture it.

This was a specialized form of battle. The procedure followed a fairly set pattern, predictable to such an extent that, by the time of the Peninsular War, it was possible to say that a given fortress could only hold out for about 40 days. Attackers needed to get the attack over before any other force could come to the relief of the defenders, and the commander of the attacking force had to take into account the possibility of coming under attack himself.

The first move would be to throw a ring around the fortress, preventing anyone from getting out as well as holding off any relief attempts. Next came the process of capturing any out-works - key places in the outer defences that were designed to make it difficut to attack the main fortress. To breach the defences themselves - usually a system of high walls and ditches, designed by experts in fortification - it was a question of getting guns close enough to the chosen point of attack to be effective. They had to make a hole wide enough for the infantry to pour through and attack the defences directly.

The hitting power of a cannonball falls as range increases, simply because it loses speed due mainly to air resistance. Thus the closer the guns could get to the walls, the more damage they could do and the faster they would force a breach in the walls. But the fortress was usually well equipped with guns of its own and these were often bigger guns than those of the besieging force because they were not having to be moved about on the campaign. The attackers therefore had to work their way forward carefully to avoid the guns being destroyed by 'counter-battery' fire.

They did this by digging long trenches, or saps, that aligned diagonally forward at an angle that prevented the defenders from looking along them and seeing what was going on. Men and materials were moved forward to positions that were often developed during the hours of darkness, where guns could be emplaced on firm platforms with protection in the form of gabions. A gabion was a large wickerwork basket filled with earth or stones - these were often made using local labour. These would be stacked up on the front of the firing platform with gaps through which the guns could fire. A gabion could in fact be anything that would absorb the power of incoming shot and there is an account of one siege where the attackers found a warehouse full of baled sheeps' wool, and used these to good effect.

                                                               Woolsacks as gabions

There would often be two or three new firing positions as the batteries moved closer until they were as little as 200 yards from the walls, from which distance they could cause enormous damage, although it could also mean they were in greater danger themselves from the defenders' firepower. In addition, there would be attacks at different points on the walls to keep the defenders guessing as to the intended main attack.

Neutralizing the defenders' guns was important for obvious reasons and this was the task of field batteries, often equipped with howitzers and mortars at longer ranges. Their role was to bring fire down on the fortress's guns and on defenders who might be trying to reinforce their positions behind the expected point of breaching.

It seems remarkable, but the breaching batteries could quite accurately 'cut' a wall, literally carving out a section with vertical 'cuts' of the width they required for a breach and then cutting a line across the bottom of the section so that the whole wall slid to the ground - more often into the ditch that usually surrounded the walls. This not only got rid of the wall, but also provided a means of filling the ditch and making it a bit easier to cross.

Sunday, 15 March 2009

Gun construction in wrought iron and bronze

It seems probable that the first material used in making guns was a copper alloy similar to brass or bronze. The earliest guns in the Royal Artillery Museum are Chinese and, although one of them is an early cast iron, the other is a copper alloy piece of a type that seems to have been made for many years - it even has a production number.

These copper alloys are easier to work than iron, which requires a higher melting temperature in order to make cast iron or a skilled blacksmith for wrought iron. Casting in copper is relatively straightforward and needs little imagination, but we will come to that presently. Let's start with wrought iron.

In Europe in the days before iron could be melted, it was worked by heating it to a glowing red and hammering it on an anvil. That is how horseshoes are made and the procedure for making guns followed the same path. Manufacture began with a sheet of iron that had been hammered out from a block and then wrapped around a mandrel - a solid cylindrical block of the required calibre for the gun itself. This formed the inner 'tube' or lining of the gun. Long rods of iron made like staves were then laid out along the length of the gun and held in place by a series of iron hoops. These were slipped into place while still hot, so that as they cooled and shrank, they tightened the rods in place. This built-up construction produced a tube open at both ends. Onto one end was fitted a 'breech block', often in the shape of a beer mug, complete with a handle and a vent hole. Holding that in place was usually a suitably shaped mounting carved out of a solid block of wood, while the rest of the gun was strapped tightly to that same mounting.

This construction, using long staves and hoops, was very similar in concept to the cooper's method of making wooden casks. Another name for a cask is a barrel - hence the name 'barrel' for the long tube of a gun!

This method of making guns was extremely laborious and the guns themselves tended to leak gas pressure, especially around the breech area, and were frequently not strong enough, blowing apart and injuring the gunners who served them.

Casting guns in copper was much preferred, though copper itself was expensive and had to be imported into England from the Continent. The skills also had to be imported and it was Henry VIII who had the wealth and determination to do just that, persuading a Venetian gunfounding family, the Arcana, to come to England and start making guns for the King. The procedure was relatively simple in concept, if rather more complex in practice.

It began with the making of a maquette - an exact replica of the external dimensions of the gun, complete with decoration (see picture), made in clay. This was actually made on a former - a length of wood wrapped in coils of thin rope, then covered in clay. When the maquette had dried, it was lightly greased and then the mould was built up around it in clay. When this, too had dried, the maquette was broken out of the mould - this was where the rope coils came in, since these could easily be pulled out, together with the former, leaving just the relatively thin clay to be broken away.

The mould was then thoroughly dried before being buried in a casting pit, muzzle end upwards, for the molten metal to be poured into it. In the years before the late 18th Century, a metal rod would be placed inside the mould and secured so that the molten metal would run around it, forming the inner shape of the barrel. However, it was found that casting the piece as a solid and drilling out the bore of the gun produced a stronger barrel.

Thursday, 12 March 2009

Artillery Ammunition - Part 1: Smoothbore period

The real weapon of the artillery is the bit that does the damage, i.e. the ammunition, not the gun or mortar though, of course, the rocket is both the projector and the ammunition.

The earliest ammunition types were the war arrow, a hail of large stones and the stone cannonball. It would be difficult to say which came first, though the war arrow is the munition depicted in the earliest known image of a gun.

There seems to be no record of them being used in war, but they remained in the inventory of the Tower of London for some 200 years. They would have had to have the warhead and the fins of the same diameter as the bore of the gun and be loaded with a tampion or wad between the tail and the propellant to provide the seal that allowed the propellant to develop its pressure. Their disadvantage was that they were only effective against men or cavalry in the open and did not have the 'hitting power' of a cannonball in siege warfare.

The hail of stones was a weapon of the 'perrier' mortar and was useful in sieges for attacking people in the open, thinking themselves protected by city or fortress walls. The stone cannonball was really only a replica of the projectiles hurled by the catapult and trebuchet, but in guns it had to be cut more accurately if it was to do the job of sealing the propellant gases long enough for them to build up pressure, and of course, not to damage the gun.

When guns began to be cast in bronze, there were occasional examples of bronze cannonballs, but the more usual early shot from these guns was the stone ball with a covering of lead. The lead gave it the weight to make it carry further and yet avoided the problems in making it entirely of lead and too heavy. Too much weight produces greater resistance in the bore and could result in bursting the gun.

Once the technique required for melting iron had been discovered, guns were cast in this material, producing stronger guns that could cope with heavier ammunition and larger propelling charges. Cannonballs began to be made of iron, usually by the same people who were casting iron guns because they had both the material and the requisite skills.

Throughout the early period and right up to the end of the smoothbore period in the middle of the 19th Century, incendiary projectiles were much in evidence. They were used in siege warfare to set fire to the wooden constructions and thatched roofs found inside cities and castles. Based on a simple internal framework, the materials used to construct the fireball varied over the years, but they must have been a frightening sight for the defenders as they flew across the sky, flames burning brightly and trailing smoke.

The invention of the hollow shell led to the development of other types of ammunition. Filled with gunpowder and detonated by a long fuze, shells were very effective in causing both damage and casualties. The blast effect, with its noise and the flying fragments of the burst shell, was a new terror both in siege warfare and on the battlefield. When Henry Shrapnel packed a shell with musket balls and burst the shell above the heads of the enemy, the rain of lead balls was, in effect, a longer range version of 'canister', the dreaded hail of lead fired at close range against infantry and cavalry.

And last, the extraordinary invention of light-producing flares to illuminate the battlefield or the breach in a siege wall, including during the 19th Century a flare packed with a parachute that would take longer to fall, making it more useful.

Thursday, 5 March 2009

What's the connection between artillery and spiders?

Strange as it may seem, there is one and it's even written up in an official 20th Century pamphlet on artillery instruments.

Put very simply, spiders spin a tough silken thread that makes an excellent 'graticule' in an optical sight, such as those used in artillery instruments. Graticules are the fine lines in a sighting system that are used to lay an instrument accurately on a given point. It was found that the web of a common spider in the grounds of the Royal Arsenal could be used, and these were sought out so that long strands could be selected and wound on a frame. A short length would then be sandwiched between thin sheets of optical glass and inserted at the correct point in the lens system for the sight so that it would remain in focus when the sight was being aimed, whether at a close or a distant object.

I doubt whether it's a system still in use, though graticules remain an essential element of many types of sight and of military binoculars and telescopes. Spiders are probably considered old-fashioned - a bit like gravity, but that's another story!

Wednesday, 4 March 2009

Artillery Instruments

One of the most basic instruments used in artillery is that for determining the elevation angle of a gun. It was known from the earliest experiments with guns that a given angle of elevation together with a fixed amount of propelling charge would achieve (theoretically!) the same trajectory every time the gun was fired. Variations in the quality of the propellant, the weight of the projectile, the condition of the bore, the weather conditions etc. all affected this trajectory, but for their purposes, gunners were able largely to rely on this angle of elevation to achieve a known range.

It was therefore important to be able to set this angle on the gun. Their solution was the gunner's quadrant. This simple device had an arm that went into the barrel, a quarter circle (quadrant) measuring instrument and a plumb bob. As the gun elevated, so the plumb bob's string moved on the quadrant, allowing the gunner to read the angle.

Over time, of course, this device became gradually more sophisticated, acquiring a levelling bubble to replace the plumb bob and achieving very high accuracy by the means of precision engineering. However, in essence, that is all that a gunner's quadrant is - a means of measuring the angle of elevation of a gun's barrel.