Just some clarifications:
Yehoshua means " God's Grace" or " God's Salvation". It is not that a letter Shin just wantonly found its way into the middle of the name: these are two words, just like Jonathan means God gave, and ( he-he) Ariel means God's Lion ( Assadullah
).
Sofer is not an "Author" but a Scribe. Sofer is a person who copies Torah scrolls by hand. The use of Sofer to designate an original author is a relatively later development.
The use of "foreighners" as personal bodyguards is a venerable tradition: Kings of Jordan used Circassians ( still do), Roman Emperors often used Germans and Byzantine Emperors used Slavs or Varangians. The trick here is that all these people would not be organic to the native population and thus (presumably) less likely to take part in palace coups. Some Big Bosses paid dearly for that illusion.
Another Jewish martial art is Krav Maga: a mix of the simplest and most brutal techniques to neutralize the opponent in 2 seconds or less. Uses elements of Heaven only knows how many established systems, from ju-jitsu to muay thai, to savate, to just nasty moves. Kind of Russian Sambo on LSD.