What always amazes me is how fast we geared up. We were still in a lingering Depression with limited industrial output.
Factories making vacuum cleaners had to convert to making machine guns, car lines to making trucks and tanks. Shipyard output expanded exponentially. Turrets, treads, armor plate, propellors, nuts and bolts - literally millions of sub-assemblies had to be created across the country and shipped to the right places for assembly.
Training cadres had to be assembled and training facilities built before we could start churning out pilots, navigators, gunners, infantrymen, tankers, artillerymen, sailors of all skills and the whole slew of mechanics, medics, cooks, clerks - all of the support personnel in the numbers needed.
And all of this was done in the space of roughly 3 years and 9 months - Dec. 8th, 1941 through Sept. 2nd, 1945, or 45 months.
The Manhattan project started with some theories and a barren desert. Before anything could be done an entire town had to be created in the middle of nowhere - houses, streets, sewers, electric lines - just to house the workers neeeded. When that was done they could get down to actually making a working atomic bomb. All under the strictest security. From start to a finished bomb took 22 months.
And all of the above was accomplished without email or computers. Phones, snail mail and slide rules were the tools of the trade.
Hell, a simple computer software upgrade can take us 6 months. One installation of a new system took over 2 years to get it right and it wasn't even that complicated of a system.
It is amazing what a country can do when its entire efforts are directed toward one goal.
