Also, how did identification work when crossing borders?

Half polish and interested to learn more about the country's history past beyond what Wikipedia can show me...thanks in advance?

Why does New York have a population of 8.3 million when other cities of around the same age (e.g. Philadelphia, Boston) have far less. Los Angeles, the second most populous city, has half the population. What's up?

was hitler's famous moustache a popular look during his lifetime or was he starting a new trend?

I'm a tenth grader and since 5th grade, history has been my strongest subject. Today I was talking to one of my old history teachers who had read over a paper I wrote about Sam Houston and Thomas Hart Benton and he told me that I wasn't really analyzing the history, I was just reciting it. He told me that without understanding motivation in history and without interpreting the actions of the people, history was useless. So I was wondering how I can go from just writing a paper about what happened to a point where I am actively thinking about and analyzing the past with complexity. I hope to be a historian myself someday, so I'd like to know how to start thinking about history in a way that I can start going beyond comprehesion and how to ask the right questions.

I have seen many different theories on why people went from roaming to staying put and farming. I was wondering if this is a highly debated topic or if there is a widely accepted answer I am unable to find. Thanks!

In regards to pain, hospitalization, chances of recovery, etc. Anything you want to throw on the topic!

I know the basics, but no sources (that I can find) go into much detail.

EDIT: And by basics, I mean: millet system, centralized government, large sphere of influence, flourishing economy, etc. And by "previous empires", I mean particularly the Safavid and Mughal empires.

I'm trying to identify the main themes in French history from 1945 to present. I'd say social development and social hardship are two important themes: As per the rebuilding of the welfare infrastructure post-war and the social hardships/unrest which are characterised by riots in France (1968, 1990s, 2005) - as they are generally founded on unemployment, pay disputes and concepts of a "tale of two cities" within Paris and its suburbs.

Furthermore I'd say economic changes in France are important and relevant to these points, as with the Gaullist sentiment in politics during the 1968 of economy being more important than social issues - Even perhaps to say it was a modernised society living largely with social elements of the 1800s under the rule of Charles de Gaul's traditional sentiments as president.

I'd love for anyone more knowledgeable to chime in here, nothing too in depth but I'm struggling to see many/any others significant recurring themes. Thanks!

Any insight on other rank names is welcome, but I am most curious about 'Privates'.

Human remains were frequently made into medicines and put into food in Europe. How did they understand such actions as being different than what native peoples did?

I'm referring to the front lines of a Legion, in combat. How well did they actually hold together under say, a barbarian charge. In the movie Gladiator for example, they don't at all. They break apart into individual melee immediately. However in everything I've read, the Legion's greatest strength was the cohesiveness of their battle lines.