With the Crimea so central to the news these days, Al-Arabiya reminds us that Egypt fought in the Crimean War as an ally of the Ottoman Empire. The title is a little overstated: "Arab Involvement in Crimean War 'Erased from History'". Not really, except insofar as the Crimean War itself (1853-1856) has been largely forgotten. In the English-speaking world most people know it, if at all, only for the charge of the Light Brigade, or perhaps Florence Nightingale. But it began as a conflict between Russia and the Ottomans, with Britain and France siding with the Ottomans.
Though Egypt was effectively self-governing from Muhammad Ali's time, it was still nominally under Ottoman suzerainty, and the Sultan requested naval and ground forces support from Egypt, and also from Tunisia. Details of the Tunisian contribution are rather scanty, but the Egyptian role is fairly well known; it was written about by the scholarly Prince Omar Toussoun; and there's even a web page dealing with Egyptian uniforms in the Crimea. On the other hand, Zeinobia laments on her blog that most Egyptians have never heard of this episode.
Actually, the involvement in the Crimean War is probably better known than Egypt's dispatch of a battalion to fight for the Emperor Maximilian in Mexico a decade later.