The first fatalities of what would become known as the Cold War come during the 1948 Berlin Blockade. Defeated Germany had been carved up by the Allies with essentially America and Britain controlling the western part, and the Soviets, the eastern. Soviet attempts to gain complete control of the capital, by blocking road and rail access, are defeated by the Berlin Airlift when America and Britain fly in fuel and food. By its end in August 1949, over 60 air-men had died in crashes but over two million Berliners had received over 2 million tonnes of supplies.
But the American sense of success, however, is short-lived. At the end of that month, the Soviets test their first atomic device. (And that same year, China turns communist.)
M.A.D (Mutually Assured Destruction)
The mutually assured nuclear destruction resultant if either superpower starts World War III leads to a global diplomatic standoff known as the Cold War. It's defined by the fact that the two powers fight each other constantly but never directly confront each other militarily.
At home, fear and paranoia become part of the American condition with children routinely doing duck and covers under their school desks in the hope it will protect them from nuclear blasts.
US Senator Joseph McCarthy exploits 'the Red Scare' (so called because of the red flag of Russia) to wholesale accuse everyone from trade union members to Hollywood stars of everything from un-American activities to being active communist agents.