Thousands of Russian troops are entering Chechnya from Ingushetia, on their way, they claim, to the Chechen capital Grozny.

A BBC correspondent on the border witnessed a column of hundreds of vehicles crossing the border.

It included tanks, armoured personnel carriers and scores of multiple launch rocket systems - awesome but inaccurate weapons that spread destruction over an area the size of a football pitch in seconds.

The reinforcements could form part of the long-awaited attack on Grozny that Russian generals have been threatening since mid-October.

But the generals' optimism, apparently shared by their troops, that the war could be over within weeks, may well be misplaced.

Bloody stalemate?

Russia's leading writer on military affairs, Pavel Felgenhauer, last week said the conflict was coming to seem more and more like a "bloody stalemate".

After a speedy advance over Chechnya's northern plains, which Chechen fighters surrendered without a struggle, the Russian troops have spent weeks inching towards Grozny from three sides, the north, west and east.

Click here to see a map of the region

They have only now, in the last few days, taken control of the towns of Sernovodsk and Assinovskaya on Chechnya's western border.

In Moscow the operation is portrayed as a deliberate attempt to slowly but steadily tie a noose around the Chechen capital, in order to minimise casualties.

Russian troops now face freezing temperatures

The generals imply that having encircled Grozny they will be able to take it quickly - and that once the capital has fallen, the rest of Chechnya will be easy to subdue.

But Mr Felgenhauer is not impressed.

Russian casualties may so far be numbered in hundreds rather than thousands, he says, but "the main rebel force has not been defeated or even seriously encountered by the army".

In an article published in the English-language daily, the Moscow Times, he wrote: "They are advancing in Chechnya at a snail's pace - an advance more reminiscent of World War I than modern warfare ... Heavy artillery pounds the same targets for days on end until everything is flattened before the infantry moves forward."

The Russian troops were able to take Chechnya's second city, Gudermes, last week, without much difficulty, though Chechens claim they still launch deadly night-time raids inside the city.

Argun next

The capture of Gudermes enables the Russians to approach the last major town beyond Grozny's eastern outskirts, Argun. If they don't face tougher resistance there, they are sure to when the battle for Grozny itself finally begins.

The Chechens have had weeks to dig trenches in the city and to prepare themselves for battle. In the last Chechen war of 1994 to 1996 they excelled in house-to-house combat and Russia only captured the city at appalling cost.

Chechens near Argun pray for victory

But despite this, and despite what the generals say, the main test for the Russian army is likely to come when they move beyond Grozny, into the mountainous south of the republic.

For the last six weeks the Russians have been advancing over largely flat terrain that is ideally suited to their tanks and artillery. It has also taken place before the worst of the winter weather.

South of Grozny there is a strip of plains, that should be relatively easy for them to capture. However their eastward progress to Kulary over the last few weeks, along the main highway crossing the breakaway republic, has been painfully slow.

But further south there is a line of villages in the foothills of the Caucasus mountains, from Alleroi in the east to Bamut in the west, which provided the rebels last time with the core of their support.

Fighting has been reported in the centre of Bamut, a village that mounted a prolonged and ferocious defence in the last war.

Beyond that the landscape gets ever more mountainous, and ever more suited to partisan warfare.

To fight in these hills might take the Russian many months, right up to next year's presidential election in June.

While the campaign has so far been popular with Russian voters, this may well change if it remains, even next spring, a "bloody stalemate".