Belarus has delivered advanced weapons to Armenia's arch enemy, Azerbaijan, even though Minsk and Yerevan are supposedly allies in the Russian-led CSTO, according to leaked documents on arms supplies, reports Politico. The cache of files sheds new light on Armenia’s decision this week to announce it will be leaving the CSTO military alliance. Now, a cache of more than a dozen letters, diplomatic notes, bills of sale and export passports seen by Politico shows that Belarus actively aided Azerbaijan’s armed forces between 2018 and 2022, as tensions peaked with Armenia. The services offered included modernizing older artillery equipment and providing new gear used for electronic warfare and drone systems. The documents include letters from the Belarusian state arms export agency to its own military-industrial firms relating to orders of state-of-the-art artillery targeting equipment for Azerbaijan as well as correspondence between the two states agreeing the purchase of Groza-S counter-drone mobile warfare stations for Azerbaijan’s armed forces. One of the diplomatic communications seen by POLITICO said that Belarusian enterprises were playing an active role “in the restoration of de-occupied territories of Azerbaijan, as well as the export of Belarusian goods and services” to the country. Azerbaijani forces also launched incursions into the territory of the Republic of Armenia proper in September 2022, taking key strategic heights. Armenia called on the CSTO for support at the time, but later accused the bloc of failing to honor its commitments after it offered only to send a fact-finding delegation. Despite on paper being an ally of Armenia, Belarusian President Alexander Lukashenko has previously described Azerbaijani President Ilham Aliyev as “our man” and said it would be “wrong” for the CSTO to oppose him. Aliyev, in turn, announced in 2022: "We have more friends in the CSTO than Armenia." However, according to experts, Belarus—one of Moscow’s closest allies—was unlikely to be acting without the tacit support of the Kremlin itself.