Answer:
The Persian Wars gave the Greeks a new feeling of confidence. The Ionian Greek cities, once subject states to the Persian king, gained their independence. The Greek world would go on to achieve great things, led by the city-state of Athens.
Explanation:
Colonial era: british
WW1: American
WW2: British (America for the atom bomb... but thats just one weapon. and they massed produced everything else really)
after that: AMERICA!!
the answer is:
1.)Skilled workers were less necessary.
2.)Fewer tasks needed to be done by hand.
3.)Inventions made production less time consuming.