Bellicose rhetoric from Baku towards Armenia and Nagorno-Karabakh is nothing new, but the volume seems to have been rising a bit lately, with Azerbaijan claiming that it could attack anywhere in Armenia, and the Armenians responding in kind:

President Serzh Sarkisian said earlier this year that an Azerbaijani assault on Armenia and Nagorno-Karabakh would trigger "serious counterattacks." Defense Minister Seyran Ohanian similarly stated in January that Armenian forces have significantly beefed up fortifications around Karabakh in recent years and are prepared for renewed fighting.

Hakobian said the unrecognized Nagorno-Karabakh Republic's army has received new military hardware and ammunition this year. "[We] have had quite a serious success in acquiring air-defense systems," he said.

So what to make of this? Anna Matveeva, writing in the Guardian, has a sensible analysis:

Encouragingly, Azerbaijan's leadership is risk-averse and not prone to impulsive moves to suit a nationalist agenda. It does not need a war to boost its popularity, because it is already popular. Rationally speaking, the war is unlikely. But military games and sabre-rattling have a tendency to get out of hand. Armenia's internal political problems can give rise to a "now or never" attitude: since the adversary appears weak, the time for a decisive push has arrived.

If it comes to it, the crucial issue is what Russia would do. There is a fashionable belief that Moscow holds the key to a Karabakh settlement, but a scenario in which Vladimir Putin calls the Armenian president, Serzh Sargsyan, and orders him to withdraw from Karabakh seems truly fantastic. In the current stalemate, Russia cannot do more than the US and France, the other Minsk group co-chairs. However, if fighting were to start, Moscow would be presented with an awkward choice as to whether it defends Armenia militarily.

On the one hand, Armenia is a member of the Collective Security Treaty Organisation, which, like Nato, operates on the collective defence principle: an attack against one member is regarded as an attack on all members. On the other hand, Moscow does not have the same problems with Baku as it has with Tbilisi: the political relationship is good, trade is rampant, Azerbaijan benefits from Russian investment and the two states co-operate in combating terrorism. In the case of deterioration, diplomatic rather than military pressure would be Moscow's most likely option.