The East Prussian Operation was a military operation by the Soviet Union to advance through and capture the German territory of East Prussia in the "Race to Berlin", as both the Soviet and Allied forces tried to reach Berlin First. This resulted in the Battle of East Prussia (13th January-25th April 1945), one of the bloodiest battles of 1945.
The East Prussian operation was itself divided into seven sub-oberations: the Insterburg-Königsberg, Mlawa-Elbing, Rastenburg-Heilsberg, Braunsburg, Samlander and Königsberg operations.
The East Prussian Operation was a full success for the Soviet Union, which then continued it's advance through Western Prussia.
Web Sources[]
http://wwii-soldat.narod.ru/OPER/ARTICLES/037-vostpruss.html (russian) https://web.archive.org/web/20070115131108/http://victory.mil.ru/war/oper/28.html (russian)