For three generations, Hawat had been responsible for Atreides House security. This meant protection for Atreides family members, anti-espionage, risk management, and various aspects of kanly. Moreover, Hawat had been entrusted with the training of the Ducal Heir Paul in the arts of war, as well as political and military strategy.
Throughout the Imperium, Hawat had a formidable reputation. He was known in the Landsraad to be both cunning and honourable. Indeed, other Great Houses coveted him for his abilities as a strategist, warrior, and trusted advisor.
The Move to Arrakis
When House Atreides was ordered to take over the planetary fief of Arrakis by Emperor Shaddam IV, Hawat had been one of the principal advisors for Duke Leto throughout the entire transition. While the Atreides were in the process of consolidating their rule over the planet, Hawat had been charged with the security of the royal compound in the city of Arrakeen, where the Atreides based their capital. During this time, Hawat saw his abilities and reputation tested when Harkonnen agents, left behind by the Baron Harkonnen, tried to assassinate Paul. However, despite Hawat offering his resignation, the Duke saw this only as a learning experience for the Mentat, advised Hawat to see it this way also, and kept him in his service.
Shortly after their arrival on Arrakis, the Duke ordered Hawat to command a raid on Giedi Prime, the Harkonnen homeworld, in order to destroy the (supposedly secret) spice hoards the Baron Harkonnen kept there. The raid was both daring and successful. It provided a morale boost of the Atreides army, which had been uncertain about its future after the move from their ancestral home of Caladan, and it served to prepare the army for the looming war with House Harkonnen, which both Hawat and the Duke were certain would come swiftly. It also demonstrated the quality of Atreides military intelligence. Most importantly, it struck at the very heart of House Harkonnen, and served as further example to the Landsraad of Atreides courage and audacity. Perhaps most brilliant of all however, was that, much to the Baron's ire, House Harkonnen could not exact retribution because the Emperor had deemed such spice hoarding as highly illegal.
In part due to the destruction of Harkonnen spice stockpiles, Hawat knew the Harkonnens would not abandon the lucrative and exclusive spice mining operations on Arrakis. Moreover, Hawat also knew that both the Baron Harkonnen and the Emperor had eyed Duke Leto Atreides with envy because of his popularity in the Landsraad. Hawat surmised - quite rightly - that if the Harkonnens were to attack Arrakis, that House Corrino would tacitly provide help, most likely in the form of Imperial Sardaukar legions, disguised in Harkonnen uniforms. Unfortunately, despite having made such an accurate analysis, as he would soon discover, Hawat had seriously underestimated how many troops the Emperor would send; Hawat's estimation was that the Emperor would send a maximum of two brigades of Sardaukar to aid the Harkonnens. The Emperor sent fifty.
A constantly suspicious man, but one who loved the Atreides, Hawat was hyper-vigilant in his protection of Atreides family members. Unfortunately, though he knew that there was a traitor in the Atreides household, Hawat mistakenly believed it to be the Lady Jessica. Even after the successful Harkonnen/Corrino attack on Arrakis, which saw House Atreides defeated, Hawat still believed that Jessica had been the one who betrayed them, instead of Dr. Wellington Yueh. This was in no small part due to the Baron Harkonnen feeding Hawat false information.
It was during the attack when Hawat had come to discover the true abilities of the Fremen. At one stage, Hawat and approximately twenty Atreides troops under his command were holed up in a cave while retreating from the Harkonnen/Sardaukar advance. Through a bond he had formed with a Fremen warrior, Hawat came to observe a skirmish between a dozen Fremen and a few Sardaukar where, after the dust had settled, only the Fremen remained standing. Moreover, Hawat also observed that a troop carrier filled with approximately 300 Sardaukar soldiers was destroyed, killing all 300 soldiers, when a Fremen flying an ornithopter made a kamikaze run at the carrier. It was through these actions that Hawat came to realise - belatedly - that the Fremen were a formidable force that could have been a powerful ally for his Duke.
In Harkonnen Service
After the Harkonnens replaced House Atreides as rulers of Arrakis, Baron Harkonnen took Thufir Hawat prisoner and forced him into his service. This was done by introducing a poison into Hawat's blood, for which only the Harkonnens maintained the antidote. Baron Harkonnen saw this as a personal victory, because of Hawat's reputation, because Hawat had foiled many of the Baron's plans against the Atreides, and because the Baron's own Mentat, Piter de Vries, had been killed by Duke Leto just before he died.
While in the service of the Harkonnens, Hawat used his considerable talents to manipulate the Harkonnens to some degree, through political manoeuvring and assassination. Hawat had attempted to create a rift between the Baron and his nephew, Feyd Rautha Harkonnen, by using a captive Atreides warrior as a means to kill Feyd in the gladiator ring. While Hawat knew the plan would ultimately fail because of the unfair advantage Feyd would give himself, the warrior had almost succeeded. Instead of facing a drugged slave, Hawat arranged for Feyd to confront a trained Atreides soldier with his capacities fully intact. As a result, the Baron's game trainer was executed for putting Feyd in danger, which left the position vacant to be filled by one of Feyd's men.
For approximately two years Hawat remained in the service of the Harkonnens, plotting and scheming in subtle ways, ultimately hoping to seek revenge against those who killed his "beloved Duke", as well as against whom he believed to be the Traitor, the Lady Jessica. Moreover, Hawat took the defeat of the Atreides as a personal failure, and therefore believed that if he continued to scheme and manipulate inside the Harkonnen House, as well as exact revenge against the traitor, he may be able to redeem himself in some way. Indeed, Hawat very nearly brought down the Harkonnens from within, playing the ambitions of the na-Baron Feyd-Rautha against his uncle. These schemes underscored the deadly cunning of Hawat, who had clearly earned his legendary reputation as a formidable political and military operative.
In 10,193 Leto's son Paul managed to restore House Atreides to power over Arrakis and ultimately wrested the Golden Lion Throne from the Corrinos. Upon discovering that Hawat had been unknowingly working against Paul under the service of Baron Harkonnen, Hawat committed suicide. He felled himself on a poison needle hidden in his left hand meant for Paul. Paul had offered him his own life for all of Hawat's serivce to House Atreides. Hawat, rather than kill the son of his beloved Duke, gave his life for the Atreides one last time. For two years Hawat had been working for the Harkonnens, helping them fight a Fremen leader named Muad'Dib who had lead an insurgency on Arrakis, only to realise that Muad'Dib was Paul himself, son of his beloved Duke. At that point, the great Thufir Hawat passed on to legend.
Behind the Scenes
Thufir Hawat was portrayed by actor Freddie Jones in the 1984 Dune movie. His death scene was filmed, but deleted from the final cut of the film. Jan Vlasák played Thufir Hawat in the 2000 Dune miniseries.