Interesting fact about the most costly (in money terms) wars: The most expensive wars in U.S. history : While the Mexican-American War cost just $2.4 billion, or 1.4% of GDP in 1847, spending on World War II accounted for nearly 36% of GDP in 1945, or $4.1 trillion. These are the most expensive wars in U.S. history.

My question is: what could they have achieved if they put those vast amounts of money to good, positive, life-building use!