Elektrogorsk, Russia - For two weeks, soldiers with chain saws felled every tree in sight.

Firefighters laid down a pipe to a nearby lake and pumped 100 gallons of water every minute, around the clock, until the surface of what is known as Fire No. 3 was a muddy expanse of charred stumps.

And still the fire burned on.

Under the surface, fire crept through a virtually impenetrable peat bog, spewing the smoke that - until the wind shifted Thursday, providing what meteorologists said was likely to be temporary relief - had been choking the Russian capital this summer.

Among all the troubles that have been visited on Russia in this summer of record heat, wildfires, smoke and crop failure, perhaps none have been so persistent and impervious to remedy as the peat fires. Particularly maddening, many here say, is the knowledge that the problem is caused by humans.

As early as 1918 Soviet engineers drained swamps to supply peat for electrical power stations. That approach was abandoned in the late 1950s, after natural gas was discovered in Siberia, but the bogs were never reflooded, although the authorities are currently weighing the idea.

For now, though, firefighters here are confronted with subterranean conflagrations that are among the world's toughest fires to snuff out, according to the small community of experts on bog fires.

"Every time you think it's out, it starts smoking again," said Sergei A. Andreyev, a soldier who was tending a hose at Fire No. 3.

The only foolproof method of suppression is to reflood the bog, a tremendously difficult job.

Unfortunately for residents of the Russian capital, the region around Moscow is particularly vulnerable to peat fires. Of 10 fires burning around Elektrogorsk, or Electrical City, named for the long-ago plan to illuminate Moscow with energy from peat, four are burning in the dried-out bogs.

Peat fires typically burn a far smaller area than fast-moving forest fires. But they can burn up to 10 times more biological mass per acre than an above-ground fire. And they spew vastly more smoke.

In Russia this summer, officials have reported 26,509 fires that so far have burned about 1.9 million acres.