The Persian army had a corps, known as the guards, which consisted of 10 to 12,000 soldiers. Though they were important, in larger armies, they could be a small fraction of the overall force.
Despite the modern attempts to recreate Western sword fighting in the Middle Ages, no one knows for sure, even with good recreations out there. The Persian army is an example of the things that impact history which include weapons to use during war, and historians debate on whether to use spears or bows.