“If — or when — diplomacy fails, the will to defend eastern Aleppo will be diminished,” he said.

Many military analysts see the Admiral Kuznetsov as merely a 200-pound gorilla, and consider it a gamble to play gunboat diplomacy with a lumbering tub fit for the scrap heap. The latest excursion is only the eighth long-distance mission for the aircraft carrier, which has been something of a lemon from the start.

“I would sum up its history as ‘tortured,’” Mr. Nordenman said.

The carrier underwent repairs from 1996 to 1998, from 2001 to 2004, and in 2008, and its deck and electronic plant were replaced in the past two years, according to Russian news reports.

It is expected back in dry dock after the Syria deployment because its propulsion system needs to be replaced.

Whenever it went to sea over the years, the Admiral Kuznetsov was prone to accidents.

The United States Navy came to its aid during one Mediterranean training exercise in 1996, when the machinery used to distill fresh water from seawater malfunctioned, leaving its crew of nearly 2,000 sailors with a severe shortage of fresh water. The carrier polluted the Irish Sea at one point with a gigantic oil spill, and a fire on board killed a crew member in 2009.

The technology used to launch airplanes is considered obsolete. Most modern carriers fling their fighter jets skyward with a kind of catapult, allowing them to carry a full contingent of fuel and weapons. Planes launched from the Admiral Kuznetsov wobble aloft from a sort of ski jump, forcing them to take off without a full load.

The warship will hug the Syrian coastline, allowing planes to perform bombing runs and return to the ship’s deck before running out of fuel, according to an unidentified source cited by the Tass news agency.

The deployment will include the first of the new MiG-29K/KUB fighters, a modernized version of that MiG jet, and the Su-33a, as well as 15 helicopters, according to Tass. “This is a potent force,” said Prokhor Tebin, a Russian who writes a blog about the country’s navy.