History of Europe

What was the purpose of 1881 Austro-Serbian Alliance how is this similar to Dual Alliance?

The Austro-Serbian Alliance of 1881 was a secret defensive pact between Austria-Hungary and the Kingdom of Serbia. Its main purpose was to prevent Russia from expanding its influence in the Balkans and gaining access to the Adriatic Sea. This alliance was similar to the Dual Alliance between Austria-Hungary and Germany, which had been formed in 1879 to counter Russian expansionism in the Balkans and to maintain the territorial status quo in Europe. Both alliances were part of a complex system of alliances and ententes that developed in Europe in the late 19th and early 20th centuries, leading up to World War I.