Accounts of the Battle of Aughrim, the decisive action of the Jacobite uprisings, suggest the two armies were at roughly equal strength. The Williamite army was said to be better trained and equipped whereas the Jacobite forces were dug in to a strong defensive position on a hillside behind a bog. It would seem to suggest a relatively close-fought thing.

Indeed it seems to have been so up until the point that the Jacobite commander, Charles Chalmot de Saint-Ruhe, was killed by a cannonball. At this point an entire flank of their army collapsed very fast, allowing the Williamites to rapidly roll up and rout the remaining forces.

What I don't understand is how the death of the commanding officer could have led to such a rapid disintegration. Modern command structures were in place by this period and Saint-Ruhe had capable underlings who should have been able to take over command. Yet either this didn't happen or there are other factors at play that the brief accounts of the fighting I've read don't take into consideration. Why did the battle turn so quickly from an equal fight into a Jacobite rout?

  • 4
    Having roughly equal numbers of men is far from sufficient to justify stating it as "an equal fight". The Romans outnumbered Hannibal at Cannae - and what an equal fight that wasn't. Apr 7, 2022 at 23:25
  • @PieterGeerkens of course but the fact is that the battl was going well for the Jacobites until their commanding officer was killed.
    – Bob Tway
    Apr 8, 2022 at 3:53
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    @KillingTime thanks for this, it does a good job of explaining the failures clearly. Would you like to summarise it into an answer, which I could then accept?
    – Bob Tway
    Apr 8, 2022 at 11:32
  • The Russian assault against Napoleon's right flank was going superbly even as Davout's Corps showed up to bolster it and Soult retook the Pratzen Heights. - until suddenly it all went very VERY wrong. Apr 9, 2022 at 11:15

1 Answer 1


An article from History Ireland magazine gives a good account of the battle and the eventual collapse of the Jacobite army.

Importantly, prior to the battle,

Saint-Ruhe bolstered his army’s morale, creating a personality cult around himself with bloodthirsty promises of what the army would do to its foes

So the morale of the army was anchored on Saint-Ruhe with the consequence that his death had the potential to be taken very badly by the Jacobite forces.

Immediately before Saint-Ruhe's death, things were looking fairly good for the Jacobites:

  • The Jacobite infantry in the centre and right of the Jacobite lines had driven off the Williamite infantry attacks and was defensively secure, if not actively winning.
  • The Williamite cavalry on the Jacobite left were attacking but they were vulnerable to a Jacobite counter-attack.

Saint-Ruhe recognised this risk to his left and took personal charge of the Life Guards from Sarsfield’s wing with the aim of crushing the threat. When he was killed, the Life Guards kept his death secret (because of the risk to morale) which exposed another problem with the battle planning:

[Keeping Saint-Ruhe's death a secret] was a disastrous decision: Sheldon’s men, awaiting Saint-Ruhe’s orders, became ever more nervous as the general failed to appear. Sheldon would not order a charge as the enemy cavalry were in Dorrington’s area of responsibility and he, Sheldon, needed Saint-Ruhe’s authority to order his men there. Worse still, Saint-Ruhe had committed one of the greatest sins a commander can commit: he had not divulged his battle strategy to his senior officers. Not even Sarsfield knew the plan. Sheldon waited in vain for his general and orders.

This effectively paralyzed the defence of the Jacobite left and allowed the vulnerable Williamite cavalry to take control of that part of the battlefield. The Jacobite dragoons who had been only opposition to the Williamite cavalry were increasingly outnumbered and their commander lead them off the field of battle. This action exposed the left flank of the Jacobite army to attack by the Williamite cavalry.

The Irish defences had been designed to protect against a frontal, not a flank, assault, and the cavalry arrived so suddenly that there was no time to change positions, nor did the training and experience of the Irish infantry allow battalions to form platoons or squares to meet the cavalry, even had there been time. Cavalry charged into the infantry who ran for the hilltop as the horsemen penetrated even further.

As often happens when morale breaks in an army, without a strong leader to re-take control; cohesion disappears, panic spreads, and it becomes every man for himself. Of the Jacobite commanders, only Sarsfield kept any control of his men but that wasn't going to be enough to save the day, he merely bought time for some of the Jacobite forces to slip away.

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