According to the poster history website, this poster reverts back to gothic style artwork that is commonly used for themes of war and battles.  It is very effective because that no matter what century you live in, you understand that the knight’s armor stands for strength, fealty and honor.  These sentiments are further reinforced by the fact that all we see of this knight is his forearm and fist.  In terms of traditional illustration techniques, the arm is in the style of woodblock printing.  If you imagine the portraits created for Barnes and Noble, it’s the same deal.  Illustrators used to use woodblock printing all the time to publish their artwork in newspapers, magazines and posters.  When illustration was just becoming a popular form of art color was created by assembly line.  Individual people were assigned to work with only one color and they were in charge of adding that one color to the illustration.  It started with the majority of the illustration being black and white with just one color added (if I remember correctly the first color to be added was blue).  This is a long way of saying that this designer is reverting back to very traditional styles of illustration- black and white plus one color.  I don’t know how you would create the arm in Illustrator, and I think I would prefer and object like this to be hand-drawn.  The poster works within Gestalt principles too because the arm is leading the eye to the text.  The text, which looks like Goudy Old Style, also portrays strength.