Thufir had a strong reputation as a cunning and one of the best mentats in the universe, but in the first half of the novel it might be hard to see, as he was tested and failed. His biggest blunder was to seriously underestimate the number of Sardaukar the Emperor would send to attack; he estimated no more than 2 brigades, but in reality there were 50 brigades (or 5 legions).

Why did Thufir make such a gross miscalculation? We know that the Emperor wanted to completely annihilate House Atreides, hence the huge number of forces sent, which raises the question: what did Thufir think the Emperor wanted to do with 2 brigades?

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    I have a feeling this was addressed in the prequels, at the very least. He didn't have ALL the information to compute based on - for example, the hatred that the Emperor had for Leto, the Guild's motivations, the intentions of Bene Gesserit. Commented Mar 19, 2015 at 23:25
  • I believe it was stated (maybe not in the book but in the Lynch movie) that he underestimated the amount of money/spice (in terms of transfer of troops) the Emperor was willing to put into bringing down House Atreides.
    – Ghanima
    Commented Mar 19, 2015 at 23:25
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    @DVK Unfortunately there isn't any prequel to Dune, much as there isn't any sequel to Matrix and no Alien movie after Cameron's Aliens.
    – Andres F.
    Commented Mar 20, 2015 at 12:17
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    @AndresF. - Han shot second. From his walkie-talkee. Commented Mar 20, 2015 at 14:34

3 Answers 3


This is covered in the body of the text of Dune. In short;

  • The move against Leto was dramatic and unexpectedly aggressive
  • The cost of the operation vastly outweighed the benefit
  • No-one would have expected the Emperor to have thrown his personal support behind the Baron when he was, at least outwardly, supportive of his kinsman. Indeed, getting caught could have destabilised the entire Empire
  • Huge pressure was being brought to bear on the Emperor by the Bene Gesserit (part of the culmination of an ultra-secret plan a millennium in the making)
  • The Spacing Guild were surprisingly willing to cooperate with a large-scale invasion of Arrakis (again, Hawat could not have had the slightest clue about the threat that Paul posed to them).

Now, hiding beneath a bit of desert rock, he nodded to himself, pulled his torn and slashed tunic around him as though warding off the cold shadows.
The size of the attack.
He had always expected their enemy to hire an occasional lighter from the Guild for probing raids. That was an ordinary enough gambit in this kind of House-to-House warfare. Lighters landed and took off on Arrakis regularly to transport the spice for House Atreides. Hawat had taken precautions against random raids by false spice lighters. For a full attack they’d expected no more than ten brigades.
But there were more than two thousand ships down on Arrakis at the last count—not just lighters, but frigates, scouts, monitors, crushers, troop-carriers, dump-boxes….
More than a hundred brigades—ten legions!
The entire spice income of Arrakis for fifty years might just cover the cost of such a venture.
It might.
I underestimated what the Baron was willing to spend in attacking us, Hawat thought. I failed my Duke.

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    @andresF. - The problem was that the threat was completely disproportionate. All the planning in the world wouldn't have saved them.
    – Valorum
    Commented Mar 20, 2015 at 12:52
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    Mentats use logic to analyse data, incorrect data will lead to incorrect analysis. Richard's point above is the key factor though. There would be no point Thufir considering a totally disproportionate, overwhelming attack, because it wouldn't be possible to counter it anyway. Instead he estimated a powerful attack that it might be possible to counter. The alternative would be to advise that resistance is futile. Commented Mar 20, 2015 at 13:01
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    Yeah the threat of them doing something so expensive would have been such a small chance, fractions of a percent, that preparing for it is out of the question. Not to mention that EVEN IF they had wanted to the pure number of troops far exceeded anything the Atriedes could ever hope to counter anyway. Don't forget the Atriedes are a relatively poor great house. their home world primary export is rice and fish if i remember correctly, while harkonnens have multiple planets, and produce expensive industrial goods, as well as many other lucrative items.
    – Himarm
    Commented Mar 20, 2015 at 13:24
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    It all has to do with Jessica giving Leto a man child. The bene gesserrit were planning on just one more generation, and harkonen, atreides man child born of a bene gesserit was an unplanned occurrence that had to be dealt with swiftly before Paul could take the water of life.
    – Escoce
    Commented Mar 20, 2015 at 23:49
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    I might add that later Thufir comes to do some self-analysis because he knows that his Mentat abilities might be compromised or shaded by his hatred and repulsion of Jessica. He never really trusted her since she was bene gesserit
    – Broklynite
    Commented Mar 24, 2016 at 8:09

One more thought: remember that he was distracted by many things. The personal threat to his master, the move from one planet to another, the training of Paul. He may have guessed the extent of the betrayal had he not been tricked into believing Jessica was working for the enemy. He had two fronts at that point and, in his mind, Jessica was by far the more dangerous. Trying to outsmart a BG took time, a lot of precious time away from deciphering Harkonnen treachery.

This is a good question which has many answers; a combination of things kept him unbalanced. An unbalanced mentat was not unique. Piter de Vries....

  • Nice additional recalled item about the mistrust of Jessica. been a very long time since I read the original Dune. Commented Aug 30, 2016 at 3:21

The cost of the Arrakis invasion was insane, beyond what any intelligent leader would order. It cost more than 50 years of spice income from Arrakis mining. Basically the Baron put House Harkonnen in Hawk for the next half century.

  • Do you have any quotes or citations to back this information up?
    – user31178
    Commented Mar 24, 2016 at 4:44
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    There is a quote above in the post by Valorum. Commented Feb 29, 2020 at 21:12

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