From March to May each year, Egypt is hit by the Khamaseen/Khamsin--sandstorms that blow intermittently over the course of 50 days (normally the storms themselves only last a few hours or days at a time). These sandstorms can be extremely powerful, with winds between 35 and 87 miles per hour. As the storms hit, they can be several miles high and look like an impenetrable wall, hiding everything behind them. As noted in this chapter, for people caught in a sandstorm, the best protection is to wrap a wet cloth over their nose and mouth to prevent sand from getting in. Failure to do so can actually result in death by suffocation.
Armies traversing Egypt and North Africa have occasionally been overtaken by sandstorms, including Napoleon's troops and troops from both sides during WWII. Most famously, in 525 BC, the 50,000 man army of the Persian King Cambyses II was buried by a sandstorm while on its way to attack the Siwa Oasis. For many years, the story of the Persian army's destruction was considered to be a myth, but in 2009 Italian researchers made a breakthrough. They found bronze weapons, a silver bracelet, an earring, Persian arrowheads, and hundreds of human bones in the desert all dating to the correct time period. The researchers estimate the army is currently buried under 16 feet of sand!