The pan-Arab dream, which saw old rivals Egypt and Syria join forces, only lasted three years. It collapsed in 1961 when Syria abandoned it, although Egypt retained the title for another decade.
The United Arab Republic (UAR) partnership came about for many reasons, not least to limit the influence of communist-leaning politicians in Syria.
With support from North Yemen and elsewhere, for a time it appeared the union could be the start of a new Middle East.