The hands of Gen. Ulysses S. Grant dash off a series of written orders. A trotting horse's legs dissolve into a lithograph of the bloody Battle of Shiloh. And the young Grant trains a horse in a Midwestern meadow.
Viewers may not pay much attention to the discrepancy between these newly filmed color sequences and the black-and-white archival images in ''Ulysses S. Grant,'' a two-part installment of ''American Experience'' on PBS beginning tonight. Partly this is because the new material is artfully integrated into the old. But there is another reason. Historical re-creations, a novelty some 10 years ago, have become commonplace in TV documentaries.
Commonplace, but not universally accepted.
Last October, the World Congress of History Producers sponsored a conference in Boston in which the issue of historical re-enactments set off a heated panel discussion. ''The room was very divided,'' said Elizabeth Deane, the writer, producer and director of the second half of the Grant documentary. ''There were as many opinions there as there were people.''
Some filmmakers championed re-creations as a way to bring history alive. Others contended that the technique compromised historical authenticity. Still others took positions in between.
Mark Samels, a senior producer at ''American Experience,'' organized and moderated the discussion. ''There is a lot of soul-searching and experimentation going on in this field,'' he said. ''It's posing a challenge to every filmmaker who makes historical documentaries for television.''
At one end of the spectrum is the work of Ken Burns, who established his reputation in 1990 with ''The Civil War,'' a documentary that relied mostly on the evocative use of stills. At the other end are programs like ''The Duel,'' an ''American Experience'' episode broadcast in 2000, which recounted the fatal confrontation between Alexander Hamilton and Aaron Burr almost completely through simulated historical scenes.
The new Grant documentary lies somewhere in the middle. It enhances archival material with impressionistic sequences that refrain from showing clear views of the actors. When a stand-in for Grant, lost in thought, looks out a White House window, the scene is captured in a long shot bathed in hazy sunlight.
The filmmakers said that historical images alone would not have been sufficiently intriguing. ''I felt that using only photographs had already been done, and that it would have been like repeating Burns's 'Civil War,' '' said Adriana Bosch, who produced the first half of the program.
More enthusiastic advocates of re-enactments say the device opens a window of possibilities for documentaries. Greg Diefenbach, an executive at the documentary house Devillier-Donegan Enterprises, said that until recently, many historical subjects were off limits to documentary-makers, especially those predating photography.
''A common refrain heard in pitch meetings was, 'Well, there are no pictures,' '' Mr. Diefenbach said. ''There was a breakthrough around '98, '99, when it became acceptable to create whole worlds through re-creations, and there was a huge backlog of demand for stories that could now be done.''
Carl Byker, who directed ''The Duel,'' contends that the re-enactment technique has elevated the documentary to a new level. ''Documentaries have always been the extremely poor cousins of feature films,'' he said. ''I don't think it has to be that way. The stories are powerful enough that if filmmakers use all the techniques at their disposal, they can remain true to history but viewers won't feel like they're doing something good for themselves. They'll be totally enthralled.''
Mr. Byker prefers not to use the word re-creation or even the word documentary. He calls his projects ''nonfiction films.'' At the History Channel, executives have begun referring to some of their programs as ''docu-movies.'' Mr. Samels defined the new approach another way: ''In essence, the historical documentary has been walking toward, and in some cases right into, the room of docudrama.''
It's precisely this redefinition of the genre that troubles some in the field, Mr. Burns among them. ''If you're going to do so much re-creation,'' he said, ''you might as well be making a dramatic film on the subject. I do think there is an art to the documentary. I do believe that while there are very few rules, we're nonetheless bound by at least an attempt, as much as possible, to not do what a feature film will do.''
Even though Mr. Samels's ''American Experience'' has sometimes made expansive use of re-created scenes, he argues that filmmakers should proceed with caution.
''I think there is a distinct danger that the more we blur the line, the more we remove what we like to think of as the historical foundation on which these things are attached,'' he said. ''We really like to believe that our audiences feel comfortable that we are presenting history, and that all we are doing with these stylistic devices is enabling it to be a bit more enlivened.''
Mr. Burns has himself experimented with more extensive use of original photography in recent years. Still, he believes that archival materials constitute the bedrock of good documentary-making. ''I fear that resorting to re-creations comes from a distrust of the evidence of the past and, particularly, a lack of respect for what I believe is the power of a single image to convey complex information,'' he said.
Phil Tuckett is the producer-director of a coming History Channel documentary entitled ''My Father's Gun,'' a family memoir of three generations of New York City policemen. He is on the opposite side of the debate. ''It's not interesting to me to do a film that relies on reminiscences and still photographs,'' he said.
Although his film uses archival material and has talking heads reminiscing, the stories are depicted in dramatized scenes. ''I think to the average viewer, this approach pulls you more into the moment,'' Mr. Tuckett said. ''It's more personal.''
On one thing most documentary-makers agree: the use of re-creations in any form requires considerable taste and skill. Mr. Samels, of ''American Experience,'' said many filmmakers at the history-producers conference had been uneasy about the challenge of integrating re-enactments into their work.
For the makers of the Grant documentary, the challenge involved finding a way to make the transitions between staged scenes and archival material as seamless as possible.
''The minute you begin to pay attention to the fact that you're watching a re-creation, you're out of the story,'' Ms. Bosch said. ''It's like a magician. The second you reveal that you're doing a trick, people are going to look for what the trick is.''
Should networks and producers establish guidelines for using re-creations? Even a relative purist like Mr. Burns dismisses the idea. ''I think that the important thing that we don't do is proclaim an orthodoxy and set rigid rules,'' he said. ''I've broken my own rules from time to time. We're constantly asking our questions about what is aesthetically and ethically correct.''
Documentary filmmakers may be discovering what historians have known for a long time. ''Historians blur the lines,'' said Robert Tignor, chairman of Princeton University's history department. ''I think we're all in the business of re-creating. That's what history is. It's a reconstruction of the past as viewed by specific individuals''.
