The national debt was artificially low at the end of Clinton's term considering he spent practically nothing on maintaining our military forces. Had he been investing properly in national defense, the debt in 2000 could easily have been 4 trillion.
Considering we were then sucker punched on 9/11, 1.2 trillion to fix our military and rid the world of vermin is money well borrowed in my book.
Actually, Clinton spent close to what President Bush has spent on Defense per GDP. They both are close to 3.5 overall I think.
Carter was spending close to double that. I'm surprised it's been so low while we are fighting WWIII. We all know that War spurs other advances in technology, Health, and other areas.