In 1958, Egypt and Syria formed a sovereign union known as the United Arab Republic. The union was short-lived, ending in 1961 when Syria seceded, thus ending the union. During most of its existence, the United Arab Republic was also in a loose confederation with North Yemen (or the Mutawakkilite Kingdom of Yemen), known as the United Arab States. In 1959, the All-Palestine Government of the Gaza Strip, an Egyptian client state, was absorbed into the United Arab Republic under the pretext of Arab union, and was never restored.
What was the sovereign union with Syria known?
United Arab Republic