The arrival of US soldiers for a peacekeeper training exercise in Armenia has rankled the Russian government, which has for decades acted as the sole security guarantor for the former Soviet republic. The 10-day “Eagle Partner” exercise, which began Monday, involves 85 US and 175 Armenian soldiers and aims to prepare the Armenians to take part in international peacekeeping missions.

The exercise, while small in scale, is the latest in a series of what Russia’s foreign ministry has deemed “unfriendly actions” taken by its traditional ally.

Armenia recently sent humanitarian aid to Ukraine for the first time, and its parliament is set to ratify the International Criminal Court’s Rome Statute – meaning it would be obliged to arrest Russian President Vladimir Putin if he were to set foot in the country, which Russia has long viewed as its own backyard.

Armenia’s flirtation with new international partners has been spurred by its frustration that Russia has been unable or unwilling to defend it against what it sees as aggression from neighboring Azerbaijan, and has raised questions about Russia’s ability to retain its hold on countries and conflicts across the former Soviet empire.

Armenian President Nikol Pashinyan said his country was beginning to taste the “bitter fruits” of the “strategic mistake” of trusting Russia with near-exclusive responsibility for his country’s defense.

“Armenia’s security architecture 99.999% was linked to Russia,” he told Italian newspaper La Repubblica earlier this month. “But today we see that Russia itself is in need of weapons… Even if it wishes so, the Russian Federation cannot meet Armenia’s needs.”

Edit: As Furball commented, Pashinyan is the Prime Minister of Armenia