Beria was the longest-lived and most influential of Stalin's secret police chiefs, wielding his most substantial influence during and after World War II. He simultaneously administered vast sections of the Soviet state and served as de facto Marshal of the Soviet Union in command of the NKVD field units responsible for anti-partisan operations on the Eastern Front during World War II. Beria administered the vast expansion of the Gulag labor camps and was primarily responsible for overseeing the secret defense institutions known as sharashkas, critical to the war effort. He also played the decisive role in coordinating the Soviet partisans, developing an impressive intelligence and sabotage network behind German lines. He attended the Yalta Conference with Stalin, who introduced him to U.S. President Franklin D. Roosevelt as 'our Himmler'. Beria was promoted to First Deputy Premier, where he carried out a campaign of liberalization. He was briefly a part of the ruling 'troika' wi