The seizure of Nicolas Maduro takes the world into new territory.

Geopolitics is about to become weirder and potentially a lot more dangerous.

America's president has justified seizing the leader of a sovereign nation by drawing on the US foreign policy of the 1830s - and he says the US will now be running Venezuela for the foreseeable future.

Venezuela crisis: Follow the latest developments

What did we learn from Trump's Venezuela news conference?

To understand what is going on, get your head around the following phrase: the Donroe Doctrine.

It is obscure, but crucial to working out what has just happened - and what is likely to come next.

Doing so requires a short history lesson.

In the 1830s, then US president James Monroe had a doctrine named after him. It declared the Americas should be a US sphere of influence. Stay out of our backyard with your colonial ventures, it warned Europeans in particular.

The Monroe Doctrine has been the stuff of history books for two centuries - but at the end of last year, it was brought back to life by the White House.

Its new national security strategy referred to the Monroe Doctrine, but added what it called a "Trump Corollary": the US would not sit idly by, it said, while hostile or criminal neighbours operated and practised "chronic wrongdoing".

And now, Donald Trump has now framed his capture of Maduro in the same light.

"We have superseded it by a lot," he said of the Monroe Doctrine. "They now call it the 'Donroe Doctrine'. American dominance in the Western Hemisphere will never be questioned again."

The early 19th century may soon be calling and asking for its foreign policy back.

Read more:
Why is Trump interested in Venezuela's oil?
Analysis: Maduro's rule was disastrous

How the US operation unfolded

The Donroe Doctrine - "Don" referring to Mr Trump - has started with Venezuela but may well not stop there.

There are plenty more hostile or criminal neighbours for Mr Trump to go after in America's backyard: the cartels of Mexico, the corrupt failing regime in Cuba, the cocaine laboratories in Colombia.

Mr Trump may consider all of them fair game.

Who might he go after next?