Neither Armenia nor Azerbaijan can be confident of a rapid victory in the conflict over Nagorny Karabakh, with both geography and the risk of foreign involvement making a military breakthrough unlikely, analysts say.

Both sides inherited equipment, military doctrine and tactics from the Soviet era, while even their modern equipment comes mostly from Russia, the analysts say.

Azerbaijan can count on a larger standing army, foreign-supplied drones and a military budget that dwarfs that of Armenia. But this may not be enough to tip the balance in a hugely complex confrontation.

Fighting in one of the most combustible frozen conflicts left over from the fall of the Soviet Union erupted late last month, with calls for a ceasefire so far falling on deaf ears.

Armenians took control of the Azerbaijani region in a war that followed the collapse of the USSR and declared a breakaway republic that has never been recognised by any state.

Both sides re-equipped intensely following the war, with Azerbaijan never hiding its desire to regain control of the territory.

Nobody's winning in Karabakh
Nobody's winning in Karabakh Armenian Defence Ministry / Handout

But Azerbaijan was able to easily outspend its neighbour due to its income from hydrocarbon reserves.

Pierre Razoux, director of the Mediterranean Foundation of Strategic Studies, says that Armenia can count on a 50,000-strong military, but with the possibility of mobilising 500,000 soldiers, as well as 20,000 soldiers in Karabakh.

It has 180 tanks and 200 other armoured vehicles and above all 35 fighter jets, as well as ballistic missiles which, according to Razoux, "can hit Azeri oil installations".

Azerbaijan has a 90,000-strong standing army and a much higher number of tanks at 600, 100 of which are the modernised T-90s preferred by the Russian military.

"Its material on land is much more significant," Razoux said. It also has 100 fighter jets and S-300 air defence systems.

Azerbaijan can count on drones from its key military supplier Israel, with whom Baku has in the last years built a warm relationship, and possibly also from its main ally Turkey.

Russian-made T-90 tanks are the backbone of Azerbaijan's ground force
Russian-made T-90 tanks are the backbone of Azerbaijan's ground force AFP / Alexander NEMENOV

But the nature of the terrain in the Caucasus mountains and the fact that it is currently controlled by Armenians are major factors counting against rapid Azeri progress.

"The mountainous terrain here, the increasingly deadly heavy weaponry, close proximity of villages and towns to the conflict means that it is very hard for one side to 'win' any military contest," commented Tom de Waal, an expert on the Caucasus and senior fellow at Carnegie Europe.

But the role of foreign powers also points towards a long, drawn-out and grinding conflict.

Most importantly, ex-Soviet master Russia has never taken a clear side in the conflict, supplying arms to both Armenia and Azerbaijan.

"Russia has tried for years to show its neutrality by delivering arms to both countries and claiming to maintain a balance of power. But it will soon have to choose," prominent Russian military commentator and deputy editor of the online newspaper Ezhednevny Zhurnal, Alexander Golts, told AFP.

Crucially, Armenia hosts one of Russia's few remaining military bases in an ex-Soviet state in Gyumri in the northwest. Unlike Azerbaijan, Armenia is a member of the Moscow-led regional security group, the Collective Security Treaty Organization (ODKB).

"Russia is the primary guarantor of Armenia's security, especially its air defence, and Azerbaijan's primary arms supplier. This allows it to have leverage on both, but it is a position that will not be tenable for very long," said Emmanuel Dreyfus, a French specialist on Russian defence issues.

A new factor in the current conflict is the strong backing that Turkey has given to its fellow Turkic neighbour, with Karabakh potentially becoming another controversial Turkish military intervention after Libya and Syria.

French President Emmanuel Macron on Thursday said hundreds of Syrian fighters had travelled to Azerbaijan via Turkey, a move he described as crossing a "red line".

While Israel has warm ties with Baku, Armenia has long enjoyed a cordial relationship with Iran, which has been accused of secretly delivering petrol to Karabakh.

The omnipresence of regional powers "may further freeze the positions of the two belligerents," said Dreyfus.