NEWS ANALYSIS : Chechnya Invasion Puts Yeltsin in Harm’s Way : Politics: Russia’s president risks presiding over a long conflict and losing allies in Parliament.

Russian President Boris N. Yeltsin has never been known to shy away from conflict, but in sending troops Sunday to subdue the fiery Muslims of the breakaway republic of Chechnya, he may have picked the nastiest fight of his life.

Consider his opponents.

Chechen men tend to feel undressed without their side arms. They wage protracted blood feuds among their powerful clans. The very name of their capital city, Grozny, means terrible or thunderous in Russian. The best-known Russian line about the Chechens, written by 19th-Century poet Mikhail Lermontov, is, “The cruel Chechen is crawling up the riverbank and sharpening his knife.”

When Chechen Foreign Minister Shamsedin Yusef said Sunday that “they cannot kill every Chechen; there are more than 1 million of us, and every one of us will fight,” it did not sound like empty rhetoric.

Of course, Caucasian daggers are no match for the might of a former superpower. But even if the Russian troops backed by pro-Moscow Chechens end up marching triumphantly into Grozny, many expect defiant Chechens to wage guerrilla warfare against Moscow for years.

And that is only one of the risks Yeltsin has incurred by sending troops toward Grozny.

When Russians comment on the tensions between Moscow and Grozny since Chechnya declared its independence in 1991, they tend to see them in the context of an infamous bit of imperial history known as the Caucasus War. For decades during the mid-1800s, the mighty czars couldn’t manage to subdue the feisty tribes of the mountainous region united under a legendary leader named Shamil.

Liberal politician Grigory A. Yavlinsky warned Sunday: “The Chechnya events are the prologue to another Caucasus War. . . . They promise decades of bloodshed. We’ll have to send our children in and bring out coffins. Russian citizens will have to shoot other Russian citizens.”

Then there is the religion factor. As Muslims, the Chechens have been inundated for months by moujahedeen from Afghanistan and other Islamic countries, to the point that Chechen President Dzhokar M. Dudayev has claimed that he no longer controls many of his fighters. The most zealous among them don green bandannas and are known as the smertniki , the suicide squads.

If Chechnya’s plight becomes bad enough, foreign policy expert Georgy Arbatov cautioned, Azerbaijan, Iran or Turkey could conceivably be persuaded to get involved.

Other analysts discount that danger. Caucasus expert Sergei Arutiunov said he does not believe that even the other small nations of the Caucasus would be willing to come to Chechnya’s aid after having seen the wreckage caused by ethnic conflicts in the Russian republic of Ingushetia and in the Georgian region Abkhazia.

“The militant mood of the other Caucasus nations” has died down, Arutiunov said. “All the awful consequences of the civil wars have demonstrated that in such wars there can be no winners.”

But the worst-case scenarios lie behind alarmist warnings by the likes of former Moscow Mayor Gavriil Popov, who declared last week that if Russia and Chechnya go to war, “all countries and republics will get dragged into this war; everything will be mixed and intermingled. And this war will go on and on. It will not end until the last Russian or Chechen dies.”

By alienating even some of his closest supporters with his militant move, Yeltsin also risks losing some of his last friends in a Parliament that is already dominated by largely hostile Communists and nationalists. Prime Minister Viktor S. Chernomyrdin barely survived a recent no-confidence vote and can little afford to lose support from normally pro-Yeltsin liberals.

In the foreign policy arena, Yeltsin is also courting trouble. Although the United States and other countries have made it clear that they consider the Chechen problem purely an internal Russian affair, they were probably not counting on a move that could turn out to be so costly in human lives.

One State Department official said Sunday that the crisis in Chechnya “might” increase calls from the U.S. Congress for a tougher line against Russia, “but I would tend to doubt it as people analyze the situation.”

That prediction of calm wasn’t borne out in initial reactions Sunday. Two senators influential in foreign affairs, Joseph I. Lieberman (D-Conn.) and John McCain (R-Ariz.), both criticized the incursion and suggested that the United States reassess its policy toward Russia.

“I think we’re seeing the resurgence of Russian imperialism,” McCain said on the CNN program “Late Edition.”

Lieberman said the troop movements “will and in fact . . . should” cause Congress to reassess its support for large-scale aid to Russia.

In addition, the decision to move troops into Chechnya heightened the danger of anti-Russian terrorist attacks in Moscow and elsewhere. Moscow police have been on special alert in the wake of Chechen threats to make their defiance known in the Russian capital, although no attacks were reported Sunday.

If angry Chechens resort to terrorism, military analyst Pavel Felgengauer said, “Russia may have to run anti-terrorist operations for years in Chechnya, as England had to do in Ireland.”

A more subtle political danger also lurks. Predictions from liberal politicians abound that terrorism combined with bloody fighting in Chechnya may serve as an excuse for hard-liners in the government to persuade Yeltsin to declare emergency rule throughout Russia. Dictatorship could then follow.

With so many dangers inherent in the decision, commentators such as Yevgeny Kiselev of Russia’s Independent Television network struggled to understand what moved Yeltsin to make it.

Kiselev noted indignantly that none of the government leaders who actually participated in the intervention plan--Defense Minister Pavel S. Grachev, Federal Counterintelligence Service chief Sergei V. Stepashin and others--have bothered to explain to the public what is going on and why.

Instead, what Russians got was a much-amended appeal from Yeltsin, released only after 9 p.m. Sunday, assuring them that the troop influx into Chechnya is meant to ensure a “political solution” to the crisis--an apparent reference to peace talks planned for today.

Yeltsin’s appeal said the troops are there to defend the civilian population from armed Chechen extremists. He also is clearly well within his rights to intervene in a region that everyone except its residents considers part of Russia. And although polls put those who favor the use of force in Chechnya in the minority, many Russians openly long for the imposition of order.

But Yavlinsky offered perhaps the most biting explanation for Yeltsin’s tactic. Yeltsin, he told Kiselev in an interview, tends to resort to force because he is no good at the tedious process of negotiations.

“He’s like a person who can’t play chess, so he kicks over the board,” Yavlinsky said.

Times staff writer Ronald Brownstein in Washington contributed to this report.