How did Yemen unite in 1990?

The unification of North and South Yemen on May 22, 1990, was driven by two primary factors. First, the discovery of oil and natural gas in the border region of Ma'rib and Shabwah made cooperation more economically rational than conflict. Second, the Soviet Union withdrew its support for South Yemen’s Marxist regime, prompting the Yemen Socialist Party to negotiate with the North to maintain its political relevance.1234

Initiated by the Saleh regime of North Yemen, the merger established a multiparty democracy with Sanaa as the political capital and Aden as the economic capital. During a 30-month transition period, power was shared between the North's GPC and the South's YSP, with Saleh serving as president and Ali Salim al-Bayd as vice president. While the unification was initially successful, the new state soon faced severe economic challenges following the Persian Gulf War, which led to the loss of foreign aid and worker remittances.14