An operational and logistical analysis of the Witch King’s attempt to storm Minas Tirith:
The goals here (operational objectives) of Sauron’s plan here absolutely check out. Minas Tirith contains most of Gondor’s military, and functionally all of its leadership and administration – its destruction could very well be war-ending. At the very least, control of Minas Tirith would open the rest of Gondor to raiding as well as enable Sauron to control the resource-rich Pelennor Fields. Delivering a powerful and effective siege (the operational objective) is very likely to lead to victory over Gondor and territorial control of it (the strategic objective). Now the question is Sauron’s plan to achieve that operational objective (we will talk about Gondor’s planning too – a little later in the series).
Now, as we’ve noted, operations are all about the problem of moving large armies. Late season Game of Thrones notwithstanding, armies do not generally teleport around the world, they have to march. That imposes all sorts of restrictions and costs on movement: where are the roads? Mountain passes? River Crossings? The terrain Sauron’s army must attack over is defined (as we’ll see) by a series of transport bottlenecks that have to be negotiated in order to deliver the siege. Then there is the issue of supplies – even orcs need to eat.
Logistics of the Army of Mordor
Looking at the logistics of moving the Army of Mordor to Minas Tirith is actually a great way to introduce some of these problems in more depth. They say ‘amateurs talk tactics, but professionals study logistics.’ Well, pull up a chair at the Grown-Ups Table, and let’s study some logistics.
The army Sauron sends against Minas Tirith is absolutely vast – an army so vast that it cannot fit its entire force in the available frontage, so the army ends up stacking up in front of the city: The books are vague on the total size of the orcish host (but we’ll come back to this), but interview material for the movies suggests that Peter Jackson’s CGI team assumed around 200,000 orcs. This army has to exit Minas Morgul – apparently as a single group – and then follow the road to the crossing at Osgiliath. Is this operational plan reasonable, from a transit perspective?
In a word: no. It’s not hard to run the math as to why. Looking at the image at the head of the previous section, we can see that the road the orcs are on allows them to march five abreast, meaning there are 40,000 such rows (plus additional space for trolls, etc). Giving each orc four feet of space on the march (a fairly conservative figure), that would mean the army alone stretches 30 miles down a single road. At that length, the tail end of the army would not even be able to leave camp before the front of the army had finished marching for the day. For comparison, an army doing a ‘forced march’ (marching at rapid speed under limited load – and often taking heat or fatigue casualties to do it) might manage 20 to 30 miles per day. Infantry on foot is more likely to average around 10 miles per day on decent roads.
Ideally, the solution to this problem is to split the army up. By moving in multiple columns and converging on the battlespace, you split one impossibly long column of troops into several more manageable ones. There is a danger here – the enemy might try to overwhelm each smaller army in turn – but Faramir has had to pull his troops back out of Ithilien, so there is little risk of defeat in detail for the Army of Mordor. The larger problem is terrain – we’ve seen Ithilien in this film and the previous one: it is heavily forested, with few roads. What roads exist are overgrown and difficult to use. Worse yet, the primary route through the area is not an east-west road, but the North-South route up from Near Harad to the Black Gate. The infrastructure here to split the army effectively simply doesn’t exist.
This actually understates the problem, because the army of Morder also needs supplies in order to conduct the siege. Orcs seem to be able to make do with very poor water supplies (Frodo and Sam comment on the foulness of Mordor water), so we can assume they use local water along the march, but that still leaves food. Ithilien (the territory they are marching through), as we have seen in the film, is unpopulated – the army can expect no fresh supplies here (or in the Pelennor beyond, for reasons we’ll discuss shortly). That is going to mean a baggage train to carry additional supplies, as well as materials for the construction of all of the fancy siege equipment (we, in fact, later see them bringing the towers pre-built – we’ll get to it). This would lengthen the army train even more.
All of that raises a second point – from a supply perspective, can this operation work? Here, the answer is, perhaps surprisingly, yes. Minas Morgul is 20 leagues (around 60 miles) from Minas Tirith. An infantryman might carry around (very roughly) 10 days or so of rations on his person, which is enough to move around 120 miles (these figures derive from K. Chase, Firearms: A Global History to 1700 (2003) – well worth a read! – but are broadly applicable to almost any army before the invention of the railroad). The army is bound to be held up a bit along the way, so the Witch King would want to bring some wagons with additional supplies, but as a matter of supply, this works. The problem is transit.
As a side note, the supply issue neatly explains the aggressive tactics the Witch king employs when he arrives at Minas Tirith, moving immediately for an assault rather than a siege. Because the pack animals which pull wagons full of food eat food themselves, there is literally no amount of wagons which would enable an army of this size to sustain itself indefinitely in a long siege. The Witch King is thus constrained by his operational plan: the raw size of his army means he must either take the city in an assault quickly enough to march most of his army back, or fail. He proceeds with the appropriate sense of urgency.
That said, the distances here are short: 60 miles is a believable distance for an army to make an unsupported ‘lunge’ out of its logistics network. One cannot help but notice the Stark (hah!) contrast with the multi-hundred-mile supply-free lunges in the TV version of Game of Thrones, which are far less plausible.
I’d like to think that the logistics of Selenoth work out well, but I’ll have to leave that for others to decide. Regardless, it’s a much more interesting take on Tolkien than most, as far as I’m concerned. And the analyst is right, it’s not a siege of the city so much as an attempt to storm its walls.