Why is warfare being rubber-stamped by Conservative and Liberal leaderships today?

Conservative or liberal -- it makes no difference. They are owned. When a politician is elected he owes his contributors (the guys who paid for the election). That is not a citizen of the US or a British subject, it is corporations that make a lot of money having wars. The will of the people is as much a myth as freedom of speech, freedom of the press. Corporations and bankers now own the west.