History is mostly a matter of dates, and the key date is always that of the last conquest. All previous conquests are then magically forgiven and forgotten.

This observation is prompted partly by the current wars in Ukraine and the Gaza Strip, but equally by the confused apology that a young student union official made on the website of a Canadian university where I spoke recently.

In Canada, the world capital of apologies, almost every public event begins with an acknowledgement that it is taking place on the “unceded territory” of one or more “First Nations” (although these statements never end with a promise that the “settlers” are going to give the territory back).

This assumption of collective historical blame even leads to declarations of personal guilt like that of the student union leader. “My name is (name withheld),” she wrote on the website. “I use she/they pronouns, and I am a settler and uninvited guest on the unceded territories of the Songhees, Esquimalt, and WSANEC First Nations.”

It would be funny if it weren’t so sad. She was born in Canada, as were her parents for several generations past, and she has no other home. She feels guilty only because she doesn’t understand how history works. The people she is apologising to were almost certainly once conquerors themselves.

There have been human beings in the Americas for at least 14,000 years. Unless the cycle of perpetual conquest and re-conquest worked differently there than it did everywhere else in the world, there can be no patch of ground that did not change hands violently several times during that long period. We just don’t know the details.

The cycle was certainly still going strong when the Europeans arrived five centuries ago. The Aztec empire in what is now parts of Mexico and the Inca empire in the Andes, both founded on conquest, were less than 300 years old. Aztec rule was so brutal that most of that empire’s subjects united with the Spanish conquistadors to overthrow it.

History always worked like that. The wars of the European great powers in the “modern” era were just variations on a theme, and nothing really changed until 1945. Then everything changed.

The politics of World War 2 were familiar, but the technologies had grown too powerful: the Second World War killed at least 40 million people and by the end they were using nuclear weapons. People were rightly frightened, and they collectively concluded that the endless wars and the constant changing of borders by force had to stop.

A lot of borders were changed immediately after that war — Poland, for example, was moved more than a hundred km west — but once the United Nations Charter went into effect in late 1945, the new rule was clear: force and even the threat of force between member states is prohibited, and above all, borders may no longer be changed by force.

This involved the freezing of many historical injustices, because almost all borders were the result of past wars, not of free votes or legal decisions. However, allowing the borders to be changed by force again would open the door to future wars ad infinitum, so they would have to stay where they are — forever.

It made sense. Indeed, there were no good alternatives, and the new rule is still being observed in the vast majority of cases even eight decades later. All the colonial borders remained intact when the European empires collapsed, including the internal borders of the old Soviet Union. As a result, there have been no more great wars, only local ones.

Some of those wars were quite big, but none has killed even 1 percent of the people who died in World War 2. Despite occasional exceptions like the Russian invasion of Ukraine and the various wars over the borders of Israel and Palestine, the new rule has been a huge success.

So why is it right to call Israelis who build Jewish settlements in the occupied West Bank “settlers”, but wrong for the young Canadian woman to see herself as a “settler and uninvited guest” in her own country? It really is a question of dates.

Canada’s borders, like those of the vast majority of countries, are older than the UN Charter and were fixed by the freeze. Those of Israel and Palestine were fixed by the UN partition of 1948 but were immediately changed by the war of that year. They can only be finally settled by mutual agreement, and seizing more land in the meantime is illegal.

Whereas the border between Russia and Ukraine already existed before 1945, was ratified by Moscow on several later occasions, and cannot legally be changed by force. There really are rules, although their enforcement is distinctly spotty.

■  Gwynne Dyer’s new book is Intervention Earth, an examination of the (terrifying) state of play in the climate game and a proposal for how to proceed. Last year’s book, The Shortest History of War, is also still available.