I recently watched a TV documentary about the Total War Research Institute, which was established in the summer of 1941 to predict the outcome of the war between Japan and the United States.

The Institute, composed was made up of a young, elite group atof people with an average age of 33,. They concluded that Japan was certain to lose due to the overwhelming difference in power between the countries.

However, Prime Minister Hideki Tojo, the former head of the army, denied the research results and presented the fabricated data about the amount of oil stocked oilpiles at a conference with the Emperor. Thereby, convincing the Emperor to commit to war, even though the Emperor had never wanted the war.

Did the Emperor not want any war, or just not want war with the US? By the time the US was pulled into the war, Japan was already fighting on many fronts.

Unfortunately, fFour years later Japan suffered a crushing defeat, as predicted by the majority of people, including the research members.

This is correct but not sure if you want to convey "unfortunately," there is an implication that had Japan won the war it would have been fortunate.

They couldn't comprehend reality and simply crazy.were overconfident (or determined to fight).

"crazy" doesn't have quite the right feel to me. It feels more like there were people that were overconfident.

In any case, the leaders were too powerless to save millions of Japanese citizens.

Don't think you need the "too" here. But this statement could be argued differently as well depending on perspectives and the story you want to tell.

Even now, 80 years after the war, we should still rethink the warlearn from history and what we should do in the future, especially about the responsibilities of leaders who we can elect.to avoid future wars. We should also consider the leaders we elect as they have a responsibility to the millions of Japanese citizens. (or .... to the billions people in the world.)

Rephrased this a bit not sure what points are more important to you.

I recently watched a TV documentary about the Total War Research Institute, which was established in the summer of 1941 to predict the (outcome of the) war between Japan and the United States.

The Institute, a group composed of young, elite groupmembers at an average age of 33, concluded that Japan was certain to lose due to the overwhelming difference in power between the countries.

However, Prime Minister Hideki Tojo, the former head of the army, denied the research's result(s)/findings and presented the fabricated data about the amount of stocked oil at a conference with the Emperor, convincing the Emperor to commitenact (or provoke; or start a) war, even though the Emperor had never wanted theo go to war.

Unfortunately, four years later Japan suffered a crushing defeat, as predicted by the majority of people, including the research members.

They couldn't comprehend reality and were simply crazy.

Or perhaps, they understood Japan's fate but they could not overcome their passion for fighting.

A more natural way to word this would be:

"[...] but they could not accept defeat without a fight."