I joined the US military literally a month before 9/11 happened. The day I felt really old was the day we started getting new enlistees who weren’t even born during 9/11. One of them told me they didn’t understand why “ancient US history” was so important in our modern military climate.
This January, Biden officially declared an end to the “War on Terror” that Bush Jr. started, which was a response to 9/11. The way our military operates today is mostly thanks to America’s response to 9/11; we evolved so much in the past 2 decades to keep up with a dangerous new decentralized threat to our nation. It’s kind of a big deal.