Documents unearthed by Politico reveal that Belarus delivered advanced weapons to Armenia’s enemy Azerbaijan even though both countries were supposed to be allies in a Russian-led international defense pact. These documents shed new light on Armenia’s decision this week to announce it will withdraw from the military alliance; a dramatic turn that will weaken the power of Russian President Vladimir Putin in former Soviet nations, as Politico notes.

Armenia is now on the verge of one historical turn to the Westincreasingly looking to Europe and NATO for protection after decades of the former Soviet republic leaning on Moscow.

The decision by Belarus – a staunch ally of Russia – to supply advanced military hardware to Azerbaijan in the period 2018-2022, giving it the upper hand in wars with its long-time rival Armenia could also have been seen as a bitter betrayal.

Both Belarus and Armenia are members of the Collective Security Treaty Organization (CSTO), a Moscow-led post-Soviet military alliance formed in 2002. In theory, members are obligated to defend each other in case of attack. But Azerbaijan left a forerunner of the bloc in 1999.

Last Wednesday, Armenian Prime Minister Nikol Pashinyan announced that his government will start the unblock processarguing that its members “they do not fulfill their contractual obligations, but they are planning a war against us with Azerbaijan.”

Now, more than a dozen letters, diplomatic notes, invoices and passports brought to light by Politico reveal that Belarus actively assisted the armed forces of Azerbaijan between 2018 and 2022, as tensions peaked with Armenia. Services offered included modernization of older equipment artillery and the provision of new equipment used for electronic warfare and drone systems.

The documents include letters from Belarus’ state arms export service to its own military and industrial companies regarding orders for state-of-the-art artillery targeting equipment for Azerbaijan, as well as correspondence between the two states agreeing to purchase the Groza-S counter-mobile stations drone warfare for the armed forces of Azerbaijan.

Neither the governments of Azerbaijan nor Belarus responded to requests for comment.

Eduard Arakelyan, a military analyst at the Yerevan Regional Center for Democracy and Security, verified that the leaked documents related to material used by Azerbaijan in recent wars, both in Nagorno-Karabakh and against the Republic of Armenia itself.

“This equipment was used with devastating results against Armenian troops and was provided by a country that is supposed to be an ally of Armenia,” he said. “In formal terms, it is a complete violation of the CSTO alliance, but, in practice, we have always known that the bloc was more supportive of Azerbaijan”