Toshiro Mifune did not receive an Oscar nomination for portraying General Makabe Rokurōta in The Hidden Fortress.
One of the reasons Toshiro Mifune is one of my favorite actors is the way he always seems to find something new to do even with similar characters. In Seven Samurai, the Samurai Trilogy, The Sword of Doom, Yojimbo, this film and even Sanjuro Mifune plays a samurai hero yet he never seems like he treading water with his character, not even in Sanjuro where he is repeating the same character from Yojimbo. In The Hidden Fortress he once again plays a sword wielding hero, but this is not just him being Yojimbo before he was Yojimbo. When he played Yojimbo Mifune very brilliantly played the character at a rather interesting distance from the drama, as the samurai of that story simply took great joy in making things go wrong for evil doers. That is not the case here for the General who must save his Princess.
Makabe is very deeply involved with saving the Princess and acts as somewhat as a father figure to her. Mifune is excellent in this time showing an utter devotion in his portrayal as there is always a palatable passion in his performance in every scene. There is none of that somewhat cynical attitude he brought in his Yojimbo performance, here he smartly shows that the General absolutely believes in what he doing and do whatever it takes to help her to safety even if it means some great sacrifice. In this performance Mifune shows that he very easily could have taken on the role of the wise Samurai, played by Takashi Shimura, in the Seven Samurai, as he exudes that stoic wisdom particularly well here. Along those same lines he also, like Shimura, he subtly brings that burden of responsibility just through his his eyes, and whole manner as the General.
In those other films I mentioned Mifune technically played a hero, but definitely not one who you instantly would describe as white knight type. That is the case here as the General is truly the good guy of the piece and the film does not hesitate in stressing that fact. Mifune very wisely goes along with it full force, and once again the physical aspects of his performance add so much. Where Kikuchiyo from the Seven Samurai seemed to barely able to stand reflected his borderline insanity, here Mifune stands up rather straight and perhaps even slightly stiffly. In this one Mifune brings the posture of a General as there is an authority just in the way he sits. The hero is there too such as when he is charging on his horse in one scene Mifune makes it something to behold as he turns it into the charge of a Knight in shining armor in the most classic sense. This makes Mifune's performance stand out particularly well, and reinforces so well the noble nature of the General.
The only times where the General does not have to purely be a hero is when he is interacting directly with the two comedic peasants Tahei (Minoru Chiaki) and Matashichi (Kamatari Fujiwara). The performances by Chiaki and Fujiwara are almost purely humorous even when the film is technically serious around them, and Mifune is very good at balancing between the two sides. Mifune acts well in playing the General as very dead pan against the antics of the two. Tahei and Matashichi sometimes help them and sometimes endanger the mission both because of their lust for gold. Mifune plays the General's reaction almost as if he is their father, as sometimes he just reacts in a slightly bemused way at their foolishness, but when they do something that might threaten the Princess in some way Mifune plays the General as a disciplinarian parent who gives them the back of his hand to bring them back into line.
Mifune also find the right balance in creating the relationship with the Princess where again he plays it like a father. Mifune keeps a certain distance in his portrayal though suggesting that he technically is her servant, but he always suggests that powerful underlying devotion to her protection. Mifune gives a particularly efficient and solid performance even though this is one of his most limited characters in a collaboration with Kurosawa in the leading role. The character is particularly straight forward in this case, and even his screen time is somewhat limited. Chiaki and Fujiwara are actually the leads of the film as well, and probably have more screen time total than Mifune does. Mifune this time mainly just needs to be one of the more straight forward of heroes. Nevertheless Mifune does a great job of it that carries the film incredibly well, even if he might not quite reach the heights of some of his other performances.