Wallachia and Moldavia were of the same stock and wished to unite as one kingdom. They made their desires known in the negotiations that resulted in the Treaty of Paris, but the Powers did not mean to create a large state on the borders of Russia which might prove a bulwark of influence for the tsar, and accordingly they denied the request. The two states found a way to accomplish their desire, soon after the conference at Paris adjourned. Meeting to select rulers each chose Alexander John Cuza simultaneously, and after hesitating two years the Powers acknowledged him as king. Thus was formed the united kingdom of Rumania; and its formation illustrated a weak point in the Concert of Europe. However much the Powers might interfere to prevent the consummation of an act they considered dangerous, they would think twice before trying to punish a Balkan state, since in doing so they might set off an explosion in the very system they were working to keep peaceful. Rumania understood this phase of the matter and took her chances. Her firm course had its reward.
The influence of Great Britain was now paramount at Constantinople. The sultan was satisfied with his ally, since he knew that of all the Powers he had least to fear from this state, which had no territories in that part of the Mediterranean and was committed to the preservation of his rule as a means of keeping Russia away from the Bosphorus. To justify herself for defending the Turk, Great Britain gave the world assurances that the sultan was about to become good. Under her insistance a series of reforms was announced, but they did not go far in the realization. Some of the promises referred to the government of the Balkans, but they were as fruitless as the others. Meanwhile French and British merchants found large profits in Turkish trade.
The tsar was humiliated by his loss of influence in the Southeast, and in 1877 he began another war against Turkey. He thought the time favorable for such action. Impeded for a while at Plevna, in Bulgaria, he at last swept the enemy before him and took Adrianople on January 16, 1878. His successes created great enthusiasm among the Serbs, Bulgars, and Rumans, who flocked to his victorious standard. The panic-stricken sultan sued for peace and at San Stefano signed a treaty which granted all that was demanded of him. Serbia, Montenegro, and Rumania were recognized as completely independent, Bulgaria as an autonomous tributary province, and Bosnia and Herzegovina were assured of important administrative reforms. Russia was awarded some territory not strictly in the Balkans, but her greatest gain was the prestige she now had as liberator of Christian states.