mericans want their military TV.

In a pop culture allegory of military might, three cable channels now feed news, information and entertainment about the armed services into millions of living rooms 24 hours a day, seven days a week.

The Military Channel, the Military History Channel and the Pentagon Channel are soliciting viewers with similar interests (war, for example), but network executives and military personnel say each channel has a distinct audience in mind, one that is reflected in the content.

"Our approach to the subject is comprehensive," said David Karp, senior vice president and general manager of the Military Channel. "We're looking at the military in a historical context, but also in a very recent context. We look back but also look to the present times and look forward."

The Military Channel, which is in about 37 million homes, is an expansion and rebranding of Discovery Wings, a niche channel run by Discovery geared toward aviation. "Probably 50 percent or more of the programming on the network was military-related," Mr. Karp said. In response to viewer demand, Discovery added combat on land and by sea.

The network made the change on Jan. 10, kicking it off with a two-hour special called "Delta Company," which followed the First Tank Battalion of the Marine Corps' Delta Company as it closed in on Baghdad during the early stages of the conflict in Iraq. The channel plans to show over 200 hours of original programming this year.

The Military History Channel is an offshoot of the History Channel, which is owned by A&E Television Networks. The company's most recent addition, the History Channel en Español, began last June. The lineup of the Military History Channel consists primarily of documentaries and feature films and includes series dedicated to the historical combat missions of the Army, Navy, Air Force, Marine Corps and Coast Guard. This month, the channel will run two-hour specials entitled, "The Complete History of the Green Berets" and "The Complete History of the Navy Seals."

The Military History Channel is in an open preview, which means that satellite and cable companies can add it at no charge. On April 2, the preview will end.

The third military network, the Pentagon Channel, is run by the Department of Defense and includes programs called "Army Healthwatch" and "In Step With Fort Riley."

"Our focus is solely the men and women in the military," said Allison Barber, the deputy assistant secretary of defense for public affairs. The news and information channel has more than two million viewers mostly military personnel and their families, Ms. Barber said.

"Sometimes we have special features that educate and help the morale," she added, referring to archival footage from old battlefields, including clips from the Korean War. "We've found that our military audience finds that interesting to see some of our old camera footage that the D.O.D. put together years ago."

Several systems, including Time Warner, are distributing the channel, which is streamed live on the Web at www.pentagonchannel.mil and beamed via satellites to military bases worldwide.

A small battle for viewers and advertisers could be looming.

Jon Mandel, the chairman of Mediacom, a media-buying agency, said he did not think there was a large enough potential audience to support three military networks.

"You're not going to do huge numbers," Mr. Mandel said. Still, he said, if the Military Channel and the Military History Channel aimed small and catered to their niches, they could both survive.

The Pentagon Channel should not pose a credible threat because it runs as a public service without advertising. Nonetheless, the Defense Department could unintentionally pull viewers away from the other channels.

Buying advertising time on niche channels can be risky because few attain an audience large enough to be rated by Neilson Media Research.

"Both Discovery and A&E have a lot of credibility with advertisers, and they have great programming, but as far as showing numbers of niche channels, it's difficult," said Shari Anne Brill, the vice president, director of programming at Carat USA in New York, an ad-buying media agency that is part of the Carat division of the Aegis Group. "You're buying something on faith."

Ms. Brill said niche channels could occasionally recruit niche advertisers but that kind of synergy would be difficult for this genre. "What are you going to be selling," she said, "Military fatigues? Gas masks?"

Mr. Karp said the Military Channel had advertising contracts with a wide array of sponsors, including automobile makers and consumer electronics companies.