Toshiro Mifune and Lee Marvin did not receive Oscar nominations for portraying the Japanese Captain and the American pilot respectively in Hell in the Pacific.
We have Lee Marvin perhaps one of the most "man's man" of the sixties as the American pilot and Marvin is sort of known for his particularly easygoing performance style even when playing technically intense characters. Marvin though is sort of the guy who just wears any hard edges so well within himself that it seems often like he does not need to try too much in that regard. That seems to free him up in a way to give perhaps a performance not always expected of the standard soldier which works very well here as the marooned man. Marvin establishes his role well in terms of the time that has likely been spent even before we meet the two men on the island. In that Marvin realizes the idea that the American has been here awhile right in his performance which lacks that outward intensity at times though he instead replaces that with this bit of insanity. Now this is not true insanity that Marvin shows but rather just the sort of partial madness inflicted on a guy who has been alone talking to himself for some time. In Marvin's delivery when he talks to himself there is a casual quality as though he's been doing for a while now to the point he doesn't give it even a second thought since he's been on the island for so long.
Then there is Toshiro Mifune, who despite being my favorite actor is not an actor who I have actively looked for his English language work. This mainly because, despite learning all the lines, he was often overdubbed poorly though since Mifune's voice is very distinct hearing anything else coming out of his mouth just seems wrong. Thankfully there is none of that nonsense here since Mifune speaks mostly in Japanese with just a few scant words in English in his real voice still. Mifune offers to begin with a more intense performance than Marvin, which is obviously something Mifune thrives with. Mifune's approach though is very much fitting to the Japanese man though given the different codes offered by their military with Mifune's character technically instructed to kill Marvin's character by the soldier's code. Mifune's approach fits that idea offering that killer instruction within his performance though he carefully mutes it ever so slightly. Mifune also portrays importantly the wear of the island in his performance as well. Mifune handles it as perhaps the second man to come though by depicting this underlying uncertainty in his physical portrayal of the Japanese Captain's manner. He has a certain fear in his intensity, as he shows the man looking for any surprises while trying to figure out his situation on the island.
The initial "battle" is very well played by both actors in that neither depict this as this cunning scheme by either man in order to get an advantage over the other. There is something more about it in both show there to be this desperation in every strike they take, and both portray that the men are as confused as when they attack as when they defend. Neither portray any hatred really in these early scenes but rather a defensive suspicion of sorts as they each make their moves against the other though usually only getting the upper hand for a moment. The two are great in the way they portray this seeking for connection even in these early stage such as in there technically most intense confrontation when they come for a duel of sorts the Japanese with a makeshift wooden samurai sword and the American with a knife. Marvin and Mifune both do well to depict a nervousness and confusion in their eyes as they reveal the men not wanting to fight to the death, while also showing that they don't know exactly what else to do either. They continue on the fighting even past this point but in the right awkward fashion. Mifune showing it as the Japanese soldier never really having an exact passion in capturing the American, just doing his perceived duty, while Marvin shows the American making a literal game out of it times almost joking around fitting to the somewhat aloof state he established that the American is in.
They eventually stop trying to best each other and begin attempting to deal with their situation of being on the desert island. The two though begin separated in this task and we are granted a bit more of each actor giving their own rendition of Castaway, just Wilson happens to be an actual person. Now in this rendition the two both thrive since they are both incredibly magnetic performers though in different ways. Marvin again continues to excel as the man who has kind of lost his mind as he brings such natural humor to the man pondering over his situation, and trying to decipher and work with his other "friend". Marvin does some talking, but often as mumbling though which wholly suits the role of the man who is more than a little lost both mentally and physically. Mifune on the other hand though conveys a greater resolve in the Japanese soldier, though is also comical in his own way as juxtaposed against Marvin's performance. Mifune though captures almost this rigorous devotion as the Japanese man attempts to prepare for his situation through this quietude of a man almost in meditation, only occasionally broken in his often amusing befuddled reactions towards whatever Marvin might be doing at a given moment. I have particular affection for Mifune's studious and calm re-raking of some sand after Marvin steps in it.
The two do begin to work together in order to make a raft to escape together and the actors work in creating the right type of chemistry with one another. The right type because there is always a certain disconnect in the verbal aspect which Marvin and Mifune portray fitting to two people who can't quite even say hello with each other to begin with, and their vocabulary doesn't improve all that much as the story progresses either. They work well in creating the physical interactions, that do actual create a chemistry there. The two begin to slowly have in through the subtle physical gestures and facial ques to create a convincing connection between the two. What is most notable though in this is how Marvin and Mifune reveal this growing ease in each other presence, as the two pull back on some of the aspects of their performances that defined the men alone, Mifune losing his intensity, and Marvin actually becoming less aloof. Both actors are remarkable though since they do end up saying so much without really saying much of anything just by making this friendship all in the unsaid, and mutual devotion that each show is focused upon helping each other get off the island. When they manage to escape the island it i inspiring not only in the accomplishment but through how believable Mifune and Marvin make the two enemies become allies. The film though reaches its unfortunate ending where the men come to another apparently deserted island. Although their good feelings continue at first they get reminders of the war, by finding an abandoned army base, and the conflict begins again. Both actors make this a painfully believable transition as well with Marvin showing the American falling back into his own world again, and Mifune is rather heart wrenching depiction of the Japanese soldiers anguish as he looks upon various images of destruction against the Japanese in a LIFE magazine. The connection is gone as Mifune shows the Japanese man falling into his own sorrows and anger related to the war, while Marvin shows the American unable to find any useful words to bridge the gap. I'd say the film could have ended with the two at the moment and would have been fitting to both characters and the terrific performances of the lead. The film though throws in an arbitrary final moment that unfortunately undercuts rather than amplifies the rest of the film. Thankfully there is the rest of the film though which contains to very impressive performances by Mifune and Marvin who both give intriguing one man shows yet manage to transition naturally into a unique two man show that results in a powerful portrait of two enemies finding common ground.