Tripartite Pact The Tripartite Pact , also the Three - Power Pact , Axis Pact , Three - way Pact or Tripartite Treaty was a pact signed in Berlin , Germany on September 27 , 1940 , which established the Axis Powers of World War II . The pact was signed by representatives of Nazi Germany ( Adolf Hitler ) , Fascist Italy ( foreign minister Galeazzo Ciano ) , and Imperial Japan ( Japanese ambassador to Germany Saburō Kurusu ) . Background and the agreement . The three nations agreed that for the next ten years they would " stand by and co - operate with one another in . . . their prime purpose to establish and maintain a new order of things . . . to promote the mutual prosperity and welfare of the peoples concerned . " They recognized each other ' s spheres of interest and undertook " to assist one another with all political , economic and military means when one of the three contracting powers is attacked " by a country not already involved in the war , excluding the Soviet Union . The pact supplemented the Anti - Comintern Pact of 1936 and helped heal the rift that had developed between Japan and Germany following the 1939 Molotov – Ribbentrop Pact between Germany and the Soviet Union . The Tripartite Pact was subsequently joined by Hungary ( November 20 , 1940 ) , Romania ( November 23 , 1940 ) , Slovakia ( November 24 , 1940 ) , Bulgaria ( March 1 , 1941 , prior to the arrival of German troops ) , Yugoslavia ( March 25 , 1941 ) , and Croatia ( June 15 , 1941 ) . Text of the pact . The Tripartite Treaty was immediately named by the Italian press " Roberto " based on the first syllables of Rome , Berlin and Tokyo . Other signatories . Hungary . The Austro - Hungarian Empire had sided with Imperial Germany during World War I and had collapsed following the defeat by the Allies . Following the Treaty of Trianon , the Kingdom of Hungary was reduced greatly in size and this caused much resentment . To assuage this resentment , Germany and Italy implemented the Vienna Awards in 1938 and 1940 and this was subsequently followed by Hungary joining the Tripartite Pact on November 20 , 1940 . Collusion was further heightened when the Fascist Arrow Cross Party later came to power . Romania . The Kingdom of Romania had joined the Allied Powers in World War I and had received Transylvania from Austria – Hungary . After Germany and Italy awarded parts of Transylvania back to Hungary and southern Dobruja back to Bulgaria and after the Soviet Union had taken Bessarabia , the Fascist Iron Guard party came to power and Romania joined the Tripartite Pact on November 23 , 1940 . This was due to the Romanian desire for protection against the Soviet Union . Slovakia . On March 14 , 1939 , after the Munich Agreement , the Slovak Republic was formed from a portion of the dismembered Czechoslovakia . Hitler invited Monsignor Jozef Tiso to be the new nation ' s leader . Soon after it was formed , Slovakia was involved in a war with neighboring Hungary . Although Slovakia had signed a " Protection Treaty " with Nazi Germany , Germany refused to help Slovakia in direct violation of that treaty . The war resulted in territorial gains by Hungary at Slovakia ' s expense . Even so , Slovakia supported the German invasion of Poland . Slovakia joined the Tripartite Pact on November 24 , 1940 . Bulgaria . The Kingdom of Bulgaria had been on the losing side in World War I , losing territory to Serbia and Greece . During World War II , Germany needed military access through Bulgaria in order to attack Greece . Adolf Hitler promised the Bulgarian Tsar Boris III that Bulgaria would receive all the territory she had lost in return for Bulgaria joining the Axis . Boris agreed and prime - minister Bogdan Filov signed the Pact on March 1 , 1941 . Yugoslavia . On March 25 , 1941 in Vienna , Dragiša Cvetković , Prime Minister of the Kingdom of Yugoslavia , signed the Tripartite Pact . On March 27 , the regime was overthrown by a military coup d ' état with British support , and the 17 - year old King Peter II of Yugoslavia seized power . General Dušan Simović became Peter ' s Prime Minister and the Kingdom of Yugoslavia initially tried to dissolve the Pact but later declared adherence to it . The initial agreement of the document also regarded Yugoslavia ' s acceptance of the free movement of German troops around the country ; this was unsatisfactory to the Führer , and resulted in the Invasion of Yugoslavia . Postponing Operation Barbarossa , the Germans simultaneously attacked Yugoslavia and Greece . Starting on April 6 , the German Air Force ( " Luftwaffe " ) bombed Belgrade for three days and nights . German ground troops ( " Wehrmacht Heer " ) moved in , and Yugoslavia capitulated on April 17 . Croatia . The Independent State of Croatia ( " Nezavisna Država Hrvatska " , or NDH ) signed the Tripartite Pact on June 15 , 1941 . Unoffical signatories . Thailand . The Kingdom of Thailand became an unofficial signatory of the Tripartite Pact at the suggestion of Japan . Thailand previously signed a military alliance with Japan and sent Luang Wichitwathakan to sign the Tripartite Pact on 15 February 1942 . Thai forces contributed to the Japanese war effort , helping out in the invasion of Burma 1942 – 1943 . Manchukuo . The Great Manchu Empire became an unofficial signatory of the Tripartite Pact at the suggestion of Japan , Zhang Jinghui the Prime Minister of Manchukuo signed the Tripartite Pact by himself on 15 February 1942 along with Thailand and the Nanking Government . China . The Reorganized National Government of China ( Nanking Government ) became an unofficial signatory of the Tripartite Pact . Other nations involved . Soviet Union . Just prior to the formation of the Tripartite Pact , the Soviet Union was informed of its existence , and the potential of its joining . Vyacheslav Molotov was thus sent to Berlin to discuss the pact and the possibility of the Soviet Union joining it . For the Soviets , they considered joining the Tripartite Pact to be an update of existing agreements with Germany . On Molotov ' s visit , he agreed in principle to the Soviet Union joining the pact so long as some details , such as Soviet annexation of Finland , could be worked out . The Soviet government sent a revised version of the pact to Germany on November 25 . To demonstrate the benefits of partnership , the Soviet Union made large economic offerings to Germany . Regardless of the talks however , the Germans had no intention of allowing the Soviets to join the pact . They were already in the preparation stages for their invasion of the Soviet Union and were committed to doing so regardless of any action the Soviets took . When they received the Soviet offer in November , they simply did not reply . They did , however , accept the new economic offerings , and signed an agreement for such on January 10 , 1941 . Finland . Military co - operation between Finland and Nazi Germany started in late 1940 after Finland had lost a significant amount of her territory to Soviet aggression in the Winter War . Finland joined Operation Barbarossa on June 25 , 1941 , starting the Continuation War . In November , Finland signed the Anti - Comintern Pact ( an anti - communist agreement directed against the Soviet Union ) with many other countries allied with Germany . Soon after this Germany suggested Finland sign the Tripartite Pact . However , the Finnish government refused , because Finland saw its war as a " separate war " from the Second World War , and it saw its objectives as different from those of Nazi Germany . Finland also wanted to maintain diplomatic relations with the Allied Powers , the United States in particular . During the Second World War , Germany asked Finland several times to sign the pact , but always the Finnish government declined the offer . Diplomatic relations between Finland and the United States were maintained until June 1944 , although the US ambassador had already been recalled earlier . The United Kingdom , however , declared war on Finland on December 6 , 1941 in support of its ally , the Soviet Union . End of the Pact . The Kingdom of Italy surrendered to the Western Allies in 1943 , marking the beginning of the end for the Tripartite Pact . While dictator Benito Mussolini ' s Italian Social Republic ( " Repubblica Sociale Italiana " , or RSI ) continued to maintain its alliance with Germany until the end of the war , the RSI was never more than a puppet state . In 1944 , both Bulgaria and Romania changed sides and became military allies of the Soviet Union . After the Slovak National Uprising in mid - 1944 , the Germans ended what little was left of the independence of Slovakia . Hungary was the last " minor " member of the pact aside from the " major " two ( Germany and Japan ) . However , by early April 1945 , Hungary was completely overrun and its pro - German dictator Ferenc Szálasi and his Fascist government were forced to flee . While technically still in operation until Japan ' s surrender , the defeat of Germany brought an end to any effective meaning of the treaty .