Although it is clearly striving to be a big play -- in scope, theme and characters -- "Kingdoms," the new historical drama that opened at the Eisenhower Theater last night, turns out to be small in dramatic rewards.

It deals with grandeur and glory, but possesses precious little of its own. Promising a magnificent clash, it delivers only a series of angry confrontations. Sumptuously costumed and boldly lit, it is a mannequin of a play.

Playwright Edward Sheehan has chosen a potentially enthralling rivalry to bring to the stage -- that of Napoleon and Pope Pius VII -- and he sees it as the archetypal struggle between heaven and earth, Christ and Caesar, the quiet might of the church and the explosive power of the conqueror. The evening's events, spread over 10 years, take place in Italy and France. But basically, it's the same conflict that Sheehan chronicles in scene after scene: two obdurate souls, refusing to budge on the issues that are crucial to them.

The sides are clear from the very start, when Napoleon summons the pope to France to preside over his coronation as emperor, and then decides in a sly burst of arrogance that only Napoleon is fit to crown Napoleon. Madness gleaming in his eye (and in Armand Assante's splendidly volatile performance, you can actually see the glints of folly), Napoleon then proceeds to make a puppet of the pope, a gold and scarlet decoration to wear with all his other medals. When the pope finally balks and excommunicates the upstart general, Napoleon has him abducted from Rome and shut up in Fontainebleau Palace, a virtual prisoner.

Act two is devoted primarily to the pope's five-year imprisonment, although periodic reports from afar indicate first the rising and then the falling military fortunes of Napoleon. However, whenever the two meet head on, which is, after all, the point of the play, it is to go over the same ground. Napoleon demands subservience of the pope, while the pope retaliates that no man can put himself above God's representative on earth. Lift the excommunication, rages Napoleon, as his empire crumbles. Repent, counters the pope, his health failing. All night long we are dealing with an impasse. What ultimately changes the equation are offstage battles that Napoleon had the bad luck to lose and Sheehan the wisdom not to try to recreate.

The playwright does attempt, however, to flesh out this standoff by suggesting that these two implacable enemies also indulged in a stormy father-son relationship. He lets the pope, in his agony, mull over memories of the sensual young peasant girl who once opened her blouse to him, before he took the vows. And he introduces Josephine in a few scenes, although her purpose seems mainly to beg Napoleon to show charity toward the pope, or else to take some honey cakes to the poor man on her own. This does not fill up his play; it merely adds some embroidery to the edges.

What passion and conviction there is to the evening is provided primarily by the lead actors -- Assante, especially. Physically, the actor looks as if he just stepped off a Delacroix canvas. The stocky body, the dense, self-absorbed brow, the tiny, hooded eyes and the lock of hair in the middle of the forehead -- it's all very convincing, indeed. But Assante has also captured the quick craftiness of the emperor, the brooding silence and the volcanic rages. It is the sort of performance that keeps you on edge, because you're never quite sure which direction it is going to go next.

Roy Dotrice has somewhat less to work with, as the pope, who is mostly a passive, long-suffering creature. But he handles the martyrdom with a frail bravery that is sometimes touching. Unfortunately, Maria Tucci, as Josephine, has next to nothing to do, other than plead with Napoleon and change costumes. She changes her costumes well.

In fact, the costumes, designed by Patricia Zipprodt, are extravagantly luxurious, as befits this tale of pomp and intimidation, and director Tony Giordano has managed to incorporate them into a fair amount of pageantry, both religious and secular. The lavishness goes only so far, though. The sweep of history notwithstanding, we are still left with two headstrong men of different but equal strengths, tugging, tugging, tugging, but dramatically going nowhere in particular.

KINGDOMS, by Edward Sheehan. Directed by Tony Giordano; sets, David Hays; costumes, Patricia Zipprodt; lighting, Paul Gallo. With Roy Dotrice, Armand Assante, Maria Tucci, Tomas Barbour, Charles White, George Morfogen, Val Kilmer. At the Eisenhower Theater through Nov. 29.