Is hindsight really 20 20?

I really have to ask this question. I was thinking of an old aphorism, “for the lack of a nail, the shoe was lost. For the lack of the shoe the horse was lost, for the lack of the horse the army was lost. For the lack of the army the battle was lost, for the lack of the battle the war was lost. For the lack of the war the country was lost.”

It seems that we like to claim that “hindsight is 20-20. But is it really? Can we say with certainty what it is that works/worked and what didn’t?
We like to think so, but I wonder. I mean think about it. We claim that if such and such did (OR didn’t) happen then this is the way things would have turned out. We think we are right and we might actually BE right, most of the time. But are we always right?
Oddly this question came up because I was splaying Risk. I was doing this on my Gameboy and I reached a point where I was ready to do a turn in for troops. I was also ready to make my final move and crush my opponent.
I thought I had enough troops to finish the job without the turn in and didn’t want to waste the time or effort to do my turn in. but I chose to do so anyway.
It turned out that in hindsight I was probably right to avoid the turn in. at least that was the way it looked. I finished the game with the entire turn in worth of forces and a small percentage of other force left over.
I first thought “see what did I say”. But then I started thinking about it. In order to win I had to split my existing troops in half. And one half of those troops were destroyed in the eastern part of North America. The “bonus” troops I had received from my turn in were actually instrumental in capturing North America, because they were able to come in from the west and smash what was left after the main army half that was there was defeated. The half I lost had blunted my opponent’s force to where the back up could finish the job.
What if the back up hadn’t been there? The other half of my force could also have been overwhelmed. Just because I had a large section of troops leftover at the end does not mean that I would have had the percentage that I ended with if the “bonus” troops hadn’t existed.
In hindsight I was thinking I was right I didn’t need those troops. But in reality I may very well have needed them.
So even in hindsight there is a question as to whether they were needed or not. But I guess in the final analysis I have to turn to another saying…
“Better to have had them and not needed them, then to not have them and need them.”