Who is Arnold Susi from The Gulag Archipelago, 1918-1956 and what is their importance?

Arnold Susi was Solzhenitsyn's cellmate in Lubyanka Prison Cell 67 and later 53, Susi believes cruelty is invariably accompanied by sentimentality, as shown by the Germans. Susi needs eyeglasses all the time. He has studied at the Faculty of History and Philology at the University of Petrograd and later law in Tartu on the way to becoming Estonia's leading lawyer, called "kuldsuu" (golden-tongued). Susi knows Russian, English, Estonian, and German and is widely read. During walks, Susi teaches Solzhenitsyn much about patience and about the true nature of the Revolution. Susi teaches him about Estonian democracy and being caught between Teutons and Slavs. They hold out against the Russians in 1918, 1940/41, and 1944. The Allies are not interested in helping them stay independent and Stalin eliminates the leadership as the Red Army invades, shipping them to Lubyanka under 58:2—desiring national self-determination.