Their alliance is fuelled by a mutual mistrust of Armenia, and Ankara routinely issues strongly-worded statements in support of Baku's ambitions to reclaim Nagorny Karabakh.
Yerevan harbors hostility towards Turkey over the massacres of some 1.5 million Armenians by Turkey under the Ottoman Empire during World War I.
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More than 30 countries have recognized the killings as genocide, though Ankara fiercely disputes the term.
Russia, which maintains close ties with Armenia, is the major powerbroker in the region. It leads the Collective Security Treaty Organisation military alliance of ex-Soviet countries that includes Armenia.
Yerevan relies on Russian support and military guarantees because its defense budget is overshadowed by Azerbaijan's spending on arms.
Oil and diaspora
Azerbaijan has recently begun leveraging oil revenues as part of a bid to overhaul its image in the West.
Baku has invested in massive sponsorship deals including with the Euro 2020 football championship, which was postponed because of the coronavirus pandemic.
Baku was due to host matches this year and Azerbaijan has held Formula 1 Grand Prix races since 2016.