Why might this parade of military equipment have taken place

A military parade is formation of alot of soldiers whose movement is restricted by close order drilling The military parade is now almost entirely ceremonial, though soldiers from time immemorial up until the late 19th century fought in formation. Massed parades may also hold a role for propaganda purposes, being used to exhibit the apparent military strength of one's nation.

the us constitution is a living document, meaning that it can be changed over time as the country changes.

porter is writing economic history because he is focusing on the cost of developing vaccines.