Look for a historic event called Paul revere between 1497 and 1781 and you will find your answer
i think you mean antibiotic ... but Alexander Fleming was the one who advanced the antibiotic (world) and was responsible for creating these categories of medicine... this affected the 20th century because millions of people use antibiotics everyday and without them... many diseases would still affect people without a cure
The Spanish then The United States
Less digging between one body of water and another, so less digging
They were in the middle of the desert. It would be a large risk to trek through such a large desert to attack them.
