The Course of a Siege

During the Sixteenth Century, siege warfare was refined into a science. Commanders quickly learned the most effective methods for reducing a fortification, and those methods became an almost standardized, step-by-step procedure. A typical siege in the age of gunpowder would proceed like this:

First the besieging army would surround the fortress with a stronghold of its own. As mentioned earlier, this stronghold would comprise lines of circumvallation (facing the country, to defend against the attack of relieving troops) and countervallation (facing the fortress itself).

The attacker would then select the point of attack, and build one or more square redoubts to act as bases for the operation. These redoubts were retreats for the workers, should the defenders make a sally. In the redoubts, they could hold off the defenders until the sally was thrown back.

Some two to five hundred soldiers would then be led (after nightfall) to within musket-range of the outworks of the fortress, and arranged in a line roughly parallel to the walls. Companies of infantry would be sent out ahead, and would lie flat on the ground in readiness to ward off sorties. The soldiers in the line would start the earthworks by each digging a trench three feet wide and three feet deep, and throwing the earth towards the fortress so as to make a parapet three feet high. Over the next few nights, the trenches would be widened to a breadth of six to twelve feet, or more if it was intended to draw carts and cannon through them. Sometimes these trenches would be so deep that the side facing the fortress had to be recessed into a firing step to enable the musketeers to level their weapons over the parapet. Trenches like these provide an AR bonus of -4 against missile attacks, provided the figures within are doing nothing. This bonus decreases to -2 if the troops in the trench are moving or involved in combat.

The first trench would then be extended towards the fortresses by means of smaller trenches called ‘saps’. Over firm, clear ground, the sap would zig-zag towards the fortress, each “arm” of the trench being between 350 and 500 feet long, and the successive arms diminishing as the approach neared the outworks. If the terrain was so tight as to prevent zig-zags, the saps would run directly towards the fortress. Timber covers and other protective measures would have to be used in these cases to minimize the murderous effects of enfilade fire from the walls.

All the while, the garrison would fight back with cannon and musketry. They would also launch sorties, which would often be brutally effective against the workers in the narrow saps. Infantry and cavalry would repeatedly surge from the outworks, not only killing the workers, but also wrecking and filling the trenches. The countervallation would usually be too far away to lend effective support to the workers, and the besiegers would often be forced to convert the actual approaches into defensive positions. Thus the trenches would often be studded every 300 to 600 feet with square redoubts, each a miniature fortress. Cavalry would often be stationed nearby in hollows in the ground or behind breastworks, to come out of hiding whenever the defenders’ cavalry made a sortie.

The heads of the saps--particularly as they drew nearer to the fortress--had to be protected from fire, or at least shielded from view (such cover would provide a -2 bonus to AR against missile fire). The sap attack would usually end 100’ from the outworks. Trenches would now be dug to right and left, with the earth being heaped up to form a musketry position and an assembly area for the coming assault.

It is important to note that, by this point in the proceedings, as many as two-thirds of the workers would have been killed by the garrison’s missile fire and sorties. Obviously, this kind of warfare was extremely expensive in terms of personnel.

The progress of the trenches would be supported by artillery fire, often from a Battarie Royale, a monster battery of up to 30 artillery pieces perhaps a quarter-mile from the fortress. These guns would continue to fire throughout the investment, varying targets as required. Later developments involved splitting the single large battery into three: a central battery, plus two smaller flanking batteries, which could bring cross-fire to bear upon a breach.

As walls got better, the cannons had to be brought in closer. In some later sieges, some pieces were brought down the saps and set up on a “counterscarp” (reinforced earthwork) as near as 100’ to the castle’s outer works.

Conventional wisdom held that it made more sense to attack the “salient” (point) of a bastion, or to attack a tower, than to concentrate on the curtain wall between bastions or towers. Even though the walls would be a much easier target, this tactic would expose the attackers to murderous cross-fire from the bastions. Four or more heavy cannon would often be mounted opposite the bastion to breach it, while supplementary batteries would be placed on either side in order to knock out the enemy cannon in the flanks of the adjacent bastions.

The next step would be to cross the ditch or moat, if the castle had one. Historically, the technique used varied from covered causeways of earth, to covered bridges floating on barrels. (By this time in a well-managed siege, the defenders’ cannon had been silenced, diminishing the vulnerability of the attackers).

If the cannon hadn’t yet breached the wall, the attacker would usually resort to mining (discussed in a subsequent section). Once a breach was opened, it would be assaulted by infantry, still supported by artillery.

In our world, by the early Seventeenth Century, the techniques for reducing a fortress had so evolved as to make the outcome almost a foregone conclusion. It wasn’t uncommon for fortified towns under siege to surrender as soon as the attackers had completed their lines of circumvallation and countervallation, the rationale being that their walls would fall eventually, and thus that it made little sense to prolong the unpleasantness.