99 points

the combination of nobles and knights created which group?

royals
peasants
vassal
lords

lords is your answer

It is not royalty, because royalty is either emperor or king, and their family.

It is not peasants, because peasants were classified towards the bottom of the 'power triangle'.

It is not vassal, because vassals usually were countries that lost to a country in a war, and was tooken over, or is a country that accepted military aid in return, paying the stronger country.

It is not lords, because lords are towards the top of the pyramid, and is directly under the king/emperor, and holds the 2nd most power.

hope this helps

answer; taking up arms to defend the nation;

i believe it is capitalists.