Because all three countries had a fascistic regime.
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Italy and Germany sent aid to Franco in the Spanish Civil War in the 1930's. Germany tested its air-force there as well. Franco was a fascist and he fought the left, including communists.
Italy Germany
Military and Economic aid from Germany and Italy.
Germany and Italy took part in the Spanish Civil War, testing their soldiers and weapons.
Italy and Germany aided General Franco in the Spanish Civil War. Italy sent soldiers and supplies and Germany used their air force in bombing raids. For them it was a practicing ground for the future wars Germany would fight.
In terms of World War II, the Spanish Civil War was important as a training ground for troops from countries that would soon be fighting each other in the coming war, especially Germany and Italy, on the one hand, and, on the other, the Soviet Union. It was also important in determining which side of the coming war might receive support from Spain. As it turned out, the Nationalist government that won the Civil War provided only minimal support to the Axis Powers.
Germany and Italy.
Spanish Nationalists who were supported by Nazi Germany, Italy, and Portugal against the Rebuplicans who were supported by the Soviet Union
none. they fought themselves
General Franco was a Fascist, and so were the regimes of Italy and Germany.
The Spanish Civil war, 1936, involved forces from Germany & Italy on the side of General Franco.