Foreign intervention sometimes played a crucial role in the outcome of the European civil wars of the early twentieth century. The Baltic states could never have beaten back the Bolsheviks without the assistance of the British and Germans. In Hungary, Rumanian invasion, not counterrevolution, overthrew the Bela Kun regime. In Finland, the Whites substantially defeated the Reds, but German assistance sealed the victory. Later, Soviet invasion guaranteed the final triumph of Tito's Yugoslav Partisans. British and American assistance was decisive in the outcome of the Greek civil war of 1944–49.

The Russian civil war seems to have been the exception. Limited intervention by Britain, France, Japan, and the United States failed to prevent the triumph of Bolshevism. The crucial intervention in Russia, however, was that of Germany, whose cooperation made possible the initial consolidation of the Bolshevik regime.

Spain had been absent from great power politics for a century and more, and had no allies, but then, except in 1898, it had not recently had need of them. On the other hand, Salvador de Madariaga, as acting representative of the Republic at the League of Nations in Geneva, had undertaken a new role virtually on his own, assuming the leadership of the lesser powers in opposition to Japanese and Italian aggression. This was the most significant new Spanish diplomatic initiative in more than a century, though it all went for naught.