Alliance

An alliance is a relationship among people, groups, or states that have joined together for mutual benefit or to achieve some common purpose, whether or not an explicit agreement has been worked out among them.

[2] The Allied Powers in World War I (also known as the Entente Powers) were initially the United Kingdom, France, the Russian Empire, Belgium, Serbia, Montenegro and Japan, joined later by Italy, Portugal, Romania, the United States, Greece and Brazil.

[10] A 2000 study in the Journal of Conflict Resolution found that allies fulfill their alliance commitments approximately 75% of the time.

[16] According to the study, "States honored their alliance commitments 66% of the time prior to 1945 but the compliance rate drops to 22% from 1945 to 2003.

"[16] One of the most profound effects of alliances can be seen in technological innovation, due to conduits of knowledge flows that are open between allies but closed between rivals.

Four countries, Bulgaria, Greece, Slovenia and Turkey, preferred Russia, despite being members of NATO.

Allies Day, May 1917, National Gallery of Art
Field Marshal Bernard Montgomery decorates Soviet Marshals and generals at the Brandenburg Gate in Berlin , 12 July 1945.
Map indicating international preferences for principal ally in the case a country were attacked, as of 2017.