The halves of “Che” are mirror images. The first, though it flashes back to Guevara’s early acquaintance with Mr. Castro in Mexico and forward to his visit to New York for an appearance at the United Nations in 1964, is essentially the chronicle of a successful insurgency. It follows Mr. Castro, Guevara and their comrades from 1956 to 1959, through the stages of their war to overthrow the Cuban dictator Fulgencio Batista, and it dwells less on their motives and personalities than on matters of military procedure. With impressive coherence and attention to tactical detail, Mr. Soderbergh shows how Mr. Castro’s initially tiny army fought its way down from the mountains of the Sierra Maestra and ultimately routed Batista’s forces.

The second half, devoted to the guerrilla campaign in Bolivia in 1967 that ended in Guevara’s death, is equally rigorous in its depiction of a failed revolt. Though Guevara tried, in a new context, to apply the strategic lessons of the Cuban revolution  concentrate on the countryside; cultivate popular support; maintain discipline and cohesion in the ranks  everything went wrong. And it turned out that Guevara’s adversaries, the Bolivian army and its American advisers, had learned a thing or two about how to wage an effective counterinsurgency.

There is a lot, however, that the audience will not learn from this big movie, which has some big problems as well as major virtues. In between the two periods covered in “Che,” Guevara was an important player in the Castro government, but his brutal role in turning a revolutionary movement into a dictatorship goes virtually unmentioned. This, along with Benicio Del Toro’s soulful and charismatic performance, allows Mr. Soderbergh to preserve the romantic notion of Guevara as a martyr and an iconic figure, an idealistic champion of the poor and oppressed. By now, though, this image seems at best naïve and incomplete, at worst sentimental and dishonest. More to the point, perhaps, it is not very interesting.

But “Che” itself is interesting, partly because it has the power to provoke some serious argument  about its own tactics and methods, as well as those of its subject. Whether American audiences will have a chance to participate in that argument is, for the moment, an open question. The mood here among buyers has been extremely cautious, and as of this writing, distributors have balked at spending $8 million to $10 million (the reported asking price for “Che”) on a 258-minute movie to be released in two parts, with subtitles.

Image Samantha Morton and Philip Seymour Hoffman in Synecdoche, New York, a Cannes entry looking for love in a marketplace of commitment-shy distributors. Credit... Cannes Film Festival

This is one of the frustrations of Cannes, for American critics at least. We see lots of fascinating movies  not all good, but very few completely worthless  and then wonder if we, or our readers, will ever see them again. I’m not in the movie business (a mutually beneficial arrangement, believe me), and not inclined to speculate with someone else’s money. I do hope, however, that sometime in the near future I can take part in the long and contentious conversation that “Che” deserves, and also see how my own initial ambivalence about the film resolves itself.