Ter-Petrosyan led Armenia alongside Defense Minister Vazgen Sargsyan through the Nagorno-Karabakh War with neighboring Azerbaijan. The initial post-Soviet years were marred by economic difficulties, which had their roots early in the Karabakh conflict when the Azerbaijani Popular Front managed to pressure the Azerbaijan SSR to instigate a railway and air blockade against Armenia. This move effectively crippled Armenia's economy as 85% of its cargo and goods arrived through rail traffic. In 1993, Turkey joined the blockade against Armenia in support of Azerbaijan.

When did Turkey decide to become part of the blockade against Armenia?