It is WWI fighting in the Alps. Italians and Hungarians both sides ended up losing thousands of soldiers. Estimates are approximately ten thousand that were killed by avalanches. Many, many of them have never had their bodies recovered. Hence the lines about being immortal and watching forever....

White Friday was event happening in December 1916 in Alps. Series of avalanches buried hundreds of Austro-Hungarian and Italian soldiers. Many of them are still there covered in layers of ice and snow. The second part when those WW2 fighters come in, that was probably an homage to all pilots who crashed in Alps and bodies of some of them are still there just like their predecessors a generation ago.

About the planes, you are right they were WW2 planes. But from what I understand the meaning of that is that the soliders who died up there during WW1 were frozen there forever and were never possible to retrieve. So they were there even as WW2 started and raged on.

It takes place in the Alps, I think. Soldiers were killed by avalanches set off by both sides on purpose by firing shells into the snow.

On December 13th, 1916 at 5 AM, known as White Friday, a series of avalanches hit both Austro Hungarian and Italian barracks and basically buried them with everyone inside. People reported afterwards that both Austro Hungarian and Italian troops fired artillery at the loose snow on the mountains to cause avalanches on each other's side. The total death toll is unknown, but approximately 2000 soldiers died and a dozen civilians. Many of the bodies were never found. Some are being found nowadays with the ice on the mountains melting more and more due to climate change.

The 2WW planes are there because the soul has stayed there for so many years that he witnessed the 2WW battles. I love this part, it's sad and touching, he's still somewhere there, watching, alone and frozen.

Serch on white friday you find the historia background

Par and Jaokim designed the chorus to be sung along too. Fighting was in the mountains and Austrian and Italian and other fought up there.

As the already has said in the comments , its about WWI. Italian vs Austria-Hungarian forces. Avalanches buried them on the mountain. From Red Baron(Red 3 biplane) until modern times (hence modern airplanes) they remain there guarding their posts. Buried under the ice and snow.

The reason you see WWII planes near the end is because the soldiers buried during White Friday were still there under the ice and snow during WWII. Many are still there up to today.

This is why In the song they said no one will hear my story. Because very few people actually focus or know about the parts of war that happened in other places because of the focus in Germany and france

This happened WW1. Soldier spirit is seeing end of WW1 and WW2 because he is frozen in time. Around 10000 soldiers died to avalanches.