Marco Polo, Mongolians and Vikings

One of my favorite Viking kings is Olav Trygvason.
And he was a military genius.
Before he become king of Norway, he and his men worked as mercenaries for the Romans.

Many times when the Romans was not able to take a city, they hired Trygvason and his men to make it happen.

Once there was a city the Romans had under siege for a long time, but they did not find a way to finish it.
So they hired Trygvason again.

Trygvason took a look at the situation, and noticed a lot of birds flying in and out of the city all the time.
He ordered his men to catch as many as possible of this birds.
They the sat up traps and fishnet around the city.
And finally they had catch almost all the birds there.

They then tied a thin thread on the legs of each bird, and attached a little cotton ball at the end of this thread that was dipped in oil.
Then he got his men to be ready to fire up this cotton balls, and release the birds.
The first thing the birds did was to fly strait back to their nest in the city, that mostly was under the roof of the buildings there.
And pretty soon the whole city was on fire and they gave up.

Now..
For a long time i thought this was a special story that only Trygvason had done.

But last year i saw a Marco Polo TV serial(I know it is fiction)
but i was still surprised when they in this serial said that Djengis Khan did exact the same.

The story about Trygvason was rewritten around 1200 by a man named Snorri Sturluson in the Norwegian King Saga (Snorres Konge saga).
So i wonder if they both actually did the same, or if one of them have stolen the idea from the other?

No matter, i love the story and how they solved it. :)

The Stories about Trygvason is many and pretty long.
But since i love them so much, i shall write more about him later.
But i shall try to separate them with one story at the time, so it become more easy to read and remember. :)
(Source: Google images i have put together)