"The New York Times" yesterday highlighted Tehran's fears of its "increasingly aggressive separatist groups," so a rare video dug up by RFE/RL's Azerbaijani Service is an interesting reminder.Inspired by the fall of the Berlin Wall, the Popular Front of Azerbaijan called for the removal of borders between Soviet Azerbaijan and Iran on December 31, 1989 -- Azerbaijan's Day of Solidarity, which is still celebrated by Azeris around the world.The unique video taken by an amateur cameraman shows Soviet Azerbaijanis rioting along the Iranian border, destroying checkpoints, and crossing into Iranian provinces with Azeri majorities.It was an unprecedented event in the history of the Soviet Union, as borders of the Great Empire had been almost sacrosanct until then.At the time Moscow was rapidly losing control over Azerbaijan and as a result Soviet Army troops stationed along the border put up virtually no resistance. No one was killed or injured during the two-day rampage.The Kremlin used the border assault as a pretext to send troops to Baku on January 20, 1990, when more than 170 people died.The ransacking of the border was also deeply concerning for the Iranian regime. Tehran feared that the independence movement in Soviet Azerbaijan could spread to its own Azeri-populated provinces.Even though now, 20 years later, all the checkpoints and border infrastructure have been fully restored, for Iranian officials that fear has probably never completely gone away.-- Kenan Aliyev