Officially claiming to be neutral, Finland lay in the grey zone between the Western countries and the Soviet bloc. The YYA Treaty (Finno-Soviet Pact of Friendship, Cooperation and Mutual Assistance) gave the Soviet Union some leverage in Finnish domestic politics. This was extensively exploited by president Urho Kekkonen against his opponents. He maintained an effective monopoly on Soviet relations from 1956 on, which was crucial for his continued popularity. In politics, there was a tendency to avoid any policies and statements that could be interpreted as anti-Soviet. This phenomenon was given the name "Finlandization" by the West German press. During the Cold War, Finland also developed into one of the centers of the East-West espionage, in which both the KGB and the CIA played their parts. The 1949 established Finnish Security Intelligence Service (''SUPO, Suojelupoliisi''), an operational security authority and a police unit under the Interior Ministry, whose core areas of activity are counter-Intelligence, counter-terrorism and national security, also participated in this activity in some places.