"how do you know?"

And that is exactly the question allmost never being asked in (my) school. "No time for it. Here are the facts. Accept it and learn them, we will determine your future on how well you memorized them"

But to be fair, some of my teachers tried this approach as much as possible, but within the whole framework of the curriculum, not much was possible.

If history was about making the connections, those connections could be used to make predictions that could be tested.

You can, but the world is still an chaotic place, so making a forcast on human geopolitics, is like making a weather forecast. Likely valid for the next days, but increasingly bad for longer timeframes.

But one can make for example the prediction that the war in Ukraine will be going on for a little bit longer.

Weather forecasts can easily be compared to actuals, and distribution of residuals can be calculated. That’s how weather forecast models are quantitatively evaluated. A seven day weather forecast has 95% confidence interval of around plus-minus 10 degrees Fahrenheit, way better than “it’ll be like today”.

Your prediction about the war in Ukraine is not falsifiable.

Look, I am not going to make a detailed geopolitical analysis here, but there are lots of sites and institutes who do, you can check them out. The difference with weather forcast is only, that human analysis of geopolitical events often hope to influence the outcome. But the weather will come whether we think it will be sun or rain.

And the prediction about the war in Ukraine would not be "it'll be like today". The current prediction is, that russia will continue to slowly make ground and move the front lines to the west. There are actually predictions how much and where exactly. I think that gets also falsified in some institutes, but is probably classified.

Are you saying there is some classified science also called history that makes quantitative, testable, falsifiable predictions?

Maybe so, but I have no clearance and have not seen it. And it would be completely different from history I studied in school. There wasn’t a single prediction, let alone quantitative prediction with time horizon and confidence interval in any of the history books I’ve read.