William Guthrie on Tilly’s Big Tercios

Tilly (Field Marshal Johann Tserclaes, Count of Tilly) was fond of the older style big tercios. William Guthrie describes these unit in his book “Battles of the Thirty Years War: From White Mountain to Nordlingen, 1618-1635” (Guthrie, 2002). I thought I’d have a look.

There is a health warning. Guthrie’s books contain a lot of great detail. But they do get a bit a a thrashing from European experts on the Thirty Years War. That means some of the below might be open to challenge. Even with my limited insight I’ve spotted a couple of things that don’t add up. But here we go.

Tilly’s Big Tercios

Guthrie (2002, p. 9-10):

The core of an infantry formation was the “battalion” of pikes. These were normally formed in “double battalion” two files per rank, thus the depth of the formation varied according to its size. This practice was somewhat antiquated in 1631. The Protestant reformers favour a fixed depth 5-ten ranks. Similarly, the Imperial FM Basta had suggested that each infantry regiment of 3000 be divided into three battalions of 500 pike and 500 shot each, and that the pikes be formed 12 deep and 40 wide. During Wallenstein’s tenure, the Imperials seem to have experimented with such shallower formations. However, Tilly, who believed in mass, favoured the older style.

The shot were divided into three groups and placed around the pike battalion. Two equal wings, called “sleeves,” of musketeers went on each side of the pikes; their depth was equal to that of the battalion. Tilly wrote that these sleeves should never exceed 20 files, as the outlying men would be too far away to be protected by the pikes. Three to five more ranks of shot were placed front of the whole mass; those before the pikes should be light arquebuses. The whole would comprise a solid block of men, the pike center surrounded on three sides by shot. This massed formation was called the tercio, after the term for regiment.

The key points are:

  • For imperial units (FM Basta)
    • the basic unit contained 500 pike and 500 shot (we see an exception to that below)
    • The central pike block was formed 12 deep and 40 wide (480 men, close enough to 500 men)
  • The shot formed up on the front and both flanks of the pike block
  • The “sleeves” of shot were the same size and formed the same depth as the pikes (so 12 deep for Imperials)
  • There were also “three to five more ranks of shot” to the “front of the whole mass” (unclear if that means the pikes or everybody)

The Spanish/Imperial infantry unit, or regiment, was indeed a tercio. And Guthrie rightly equates a tercio with a regiment, as they are a similar size and were both an administrative unit. However, the battlefield formation was not a tercio. On the battle field the tercios and regiments were reorganised into squadrons (see Renaissance Battlefield Tactics). More than one tercios or regiment might contribute to a squadron. A large tercio might form more than one squadron. Guthrie is bit loose with terms but this, the squadron, is what he terms the battalion “of 500 pike and 500 shot each”.

Guthrie is vague on the size of Tilly’s tercios. He mentions, when talking about the imperials, splitting a 3,000 man regiment into three. This might imply he views all tercios as containing 3,000 men, although that might be stretching what he says too far. 3,000 was the paper strength of tercios, was never achieved in practice, at any period. During the Thirty Years War tercios were much smaller, down to 600 men.

Guthrie also talks about a ‘”battalion” of pikes’. I suspect he just means the pike block and gives it a modern name for convenience. The Spanish did use the word battalion, but as far as I know, in this period, battalion was only used for Spanish cavalry battlefield formations.

Guthrie mentions the pikes ‘normally formed in “double battalion” two files per rank’. The imperials clearly didn’t do this as in their 1,000 man units “the pikes be formed 12 deep and 40 wide”. By my calculation a 500 man pike block in ‘double battalion’ would be about 16 ranks deep and 32 wide (512 total) making exactly “two files per rank”.


Guthrie (2002, p. 10-11) goes on to say:

[In the tercios] the pike were the formation, the shot around them were supporting skirmishers. They were expected to move to accommodate the pike. Unlike their Protestant opponents, the Catholics did not form their shot in regular ranks. It appears that they merely grouped themselves around the pike in loose files, and each man took as much time reloading and firing as he needed. There was no attempt to systematize the weapons for uniform fire. Usually the heavier, slower weapons lined up closer to the pikes and the lighter further out on the sleeves, with the lightest actually in front of the battalions, but that was all. The officers were inside the pike battalion and made little effort to direct or supervise the shot’s fire. Every man fired as he could selecting his own target. As a tercio’s sleeves might be 25 ranks deep or more, it could maintain a steady fire for over an hour. The excess depth meant that any given discharge was only 60% the theoretical maximum, however it also compensated for inefficient organization of shot. As it had a 40% “firepower cushion,” the tercio could fire while advancing in a way impossible to a more efficient, shallower formation.

That is interesting: the lighter arquebus were in front of the pikes and towards the flanks of the shot sleeves. The heavy muskets were closer to the pikes in the sleeves. Some

I’m not sure about “the tercios’s sleeves might be 25 ranks deep or more”. That might have been true 100 years earlier but wasn’t true in this period. Certainly doesn’t apply to the imperialists where the proportion of pike to shot was 500 to 500. So each sleeve would have only 250 shot. At Tilly’s maximum of 20 files, that would give only 12 in each rank, or half of what Guthrie mentions. By coincidence Guthrie says “the pikes be formed 12 deep and 40 wide” and the sleeve’s “depth was equal to that of the battalion [of pike]” so the whole formation was 12 deep, with the pikes 40 wide and each shot sleeve 20 wide.

Of course that ignores the arquebusiers in front of the pikes. Assuming the imperialist pike were 40 wide and the arquebusiers deployed in front in 4 ranks, that would make 160 (40 x 4) arquebusiers in front of the pikes. So we have to deduct this number from the sleeves; each sleeve of shot would only have 170 men (170 + 170 + 160 = 500). Assuming the sleeves are still deployed 12 deep to match the pikes, this would make the sleeves 14 files wide (14 x 12 = 168 men). Of those, 4 would be arquebus and 10 muskets, assuming a 50/50 split between those weapons.

The following diagram is what I think Guthrie is describing for his 1,000 man Imperialist “tercios”.

Guthrie - 1000 man Imperialist Tercio

Guthrie – 1000 man Imperialist Tercio

We might also have to increase the depth of the sleeves because it was 16 deep in the centre (12 pike ranks and 4 arquebusier ranks). This would mean there were only about 10 files in each sleeve.

Whatever the calculations we use the sleeves were not “25 ranks deep or more” for the imperialists. Probably 12 or 16.

But I can’t do these calculations without a size for Tilly’s big tercios.

Comparing Tercios and the Dutch system

Guthrie (2002, p. 11) compares the tercios to the Dutch infantry:

The tercio had resilience and could endure far more punishment, with far less loss of effectiveness, than its competitors. The solid mass of the tercio represented a moral power encouraging to its members and demoralising to its enemies. For all the efficiency of his linear battalions, Maurice of Nassau never challenged the Spanish tercios on even terms. His “retiring” countermarch maximized his superior firepower while avoiding close combat where solidity would become a factor.

Of course I like the acknowledgement that “the tercio had resilience and could endure far more punishment” and the observation that “Maurice of Nassau never challenged the Spanish tercios on even terms”. Dutch tactics were to avoid contact by the big tercios.

Big Tercios at the Battle of Breitenfeld

About Breitenfeld, Guthrie (2002, p. 25) says:

Tilly formed his defensive line while the enemy was still at a distance. Although outnumbered, it was still a large army, one of the largest he ever commanded. Tilly drew up his infantry in a curious manner: the 8600 Imperial foot were divided into eight battalions of approximately 1000 each, while the 12,800 League infantry formed six battalions of 2000. Either Tilly was concentrating his own veterans for offensive action and spreading the less sturdy Imperials, or the Imperials were accustomed to and preferred a smaller formation. Assuming that they were following Tilly’s dictum that each musketeer sleeve should be limited to 20 files, and given that 15 ranks of heavy musketeers were required to maintain a constant fire, no more than 600 muskets, plus 1-200 arquebuses in front of the pike, could be used effectively in a firefight. Therefore, the Imperial tercios, of up to 15000 men, were almost as efficient as the Swedish battalions, but the larger League tercios wasted half their firepower.

Ah, here we have the Tilly’s own Catholic League troops forming up in units of 2,000 men but the allied Imperialist “tercios” only had 1,000. So Tilly’s ideas about tactics did not extend to his allies.

Guthrie has no detail on how these 2,000 man tercios differ from the 1,000 man units described above. So I thought I’d have a go at a hypothesis. Here goes. ‘These were normally formed in “double battalion” two files per rank’. Using this calculation Tilly’s pike block should be 45 files and 22 ranks (990 men). The arquebus at the front are 25 files by five ranks (225 men). Each arquebus sleeve has 6 files and 22 ranks. The musketeer sleeves have 12 files and 22 ranks. So slightly wider than the imperialist tercio but nearly twice as deep.

You can’t quite see the difference when the bigger tercio is by itself so here are Guthrie’s 1,000 man imperial tercio and my 2,000 man hypothetical Tilly tercio next to each other.

Guthrie - 2000 man Catholic League Tercio with 1000 man Imperialist Tercio

Guthrie – 2000 man Catholic League Tercio with 1000 man Imperialist Tercio

Swedish Brigades

I can’t help mentioning the Swedish brigades. Earlier Guthrie (2002, p. 17) observes that Gustavus Adophus:

Finding the individual skvadrons too weak to stand up to serious attack, Gustavus hit on the idea of grouping them into “brigades” of three or four battalions. This formation, three battalions in line – the middle one is often depicted as slightly forward, like a flattened arrowhead – grouped under the command of a senior colonel, combined the efficiency of firepower of the line with the flexibility of the tercio.

Hmm, that flattened arrowhead thing isn’t actually true. As I’ve shown before, the Swedish Brigade of the Thirty Years War was either a triangle (three battalion) or a diamond (four battalion). They were deep formations with many of the shot hidden behind pike blocks, so talking about efficiency of Swedish fire is fairly dubious.


Guthrie, W. P. (2002). Battles of the Thirty Years War: From White Mountain to Nordlingen, 1618-1635. Greenwood Press.

4 comments to William Guthrie on Tilly’s Big Tercios

  • Guthrie opinions seem to be anachronistic, since it mixes Spanish TOEs which were used a century before with a situation quite different. As usual, he repeats he traditional -and long debunked- myth about how agile and flexible were the Swedish formations and tactics compared to Spanish rigid, old fashinoed tercios. It would be useful to remember that most of the Catholic League and Imperial armies were composed by native formations, which did not follow to the letter Spanish regulations (themselves in a state of almost continous change in order to adapt to the exigences of the battlefield with diminishing resources),I´d suggest fhe reading of Julio Albi de la Cuesta´s “De Pavia a Rocroi” for a more detailed analysis of the evolution of the tercios.

    • Steven Thomas

      Pablo, I agree at times Guthrie’s views appear anachronistic. This is a common problem in English sources for the pike and shot period. Authors obsess about the 3000 man tercios and contrast that to, well, everything.

      Clearly nobody in the Thirty Years War was using the official 3000 man formation of 100 years earlier. And probably nobody ever used that formation in reality – even in the Great Italian Wars – it was paper strength at best.

      But we do know the Imperialists had 1000 man formations and Tilly’s own Catholic League infantry were formed into 2000 man units. I’ve tried to tease out what Guthrie has to say about these smaller formations, formations that appeared in actual battles.

      Of course other sources might be more accurate and shed more light. Thanks for the heads up on “De Pavia a Rocroi” . I’ll have to brush off my Spanish.

  • Good analysis Steven.

    Guthrie doesn’t help things by using the word Tercio, a term used to identify an organizational unit, as a title for a battlefield formation (as do most people). The thing to remember, as you have pointed out, is that the commander of the day, organized the units as they deployed, as he wanted them.

    Neil Danskin published a work in the early 1990s for the Pike and Shot Society on the development of Spanish infantry tactics. Really worth a read if you can find a copy; I’m not really sure where mine is.

    • Steven Thomas

      I don’t think I subscribed to the P&S society in the 90s. So I’m not sure I have Danskin’s book. Shame.

      I have his book on the French Army of the Thirty Years War. It suffers for poor reproduction of the graphics but has great content.

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