Thelian was the Federation president when first contact was made with the Cardassian Union. Thelian attended a historic meeting with the Legarans at Vulcan in 2327, to which the Cardassians had been invited as observers. However, Cardassian efforts to sabotage the talks and assassinate the Legaran delegation, though disavowed by the Cardassian government, served to damage diplomatic processes, leading eventually to the Cardassian Wars. (TOS comic: Enter the Wolves)