Perhaps we should have a little background info of what all this is about?
The battle of Helgoland or Heligoland if you will, was the largest naval engagement of the Second Schleswigan War 1864 and it took place towards the end of that war.
It's interesting to historians because the ships were among the very latest designs in warships, and tactics with ships independent of the wind was very much in it's infancy.
As a consequence of Preussia and Austria siding with Schleswig & Holstein against Denmark in 1864, Austria send a small squadron to the Northsea, consisting of two steam frigates. Here they would meet with five Preussian gunboats. The Preussian navy at the time was very small and consisted only of coastal vessels and since the Danish navy blocked the German ports there was a limit to what they could send out to support the Austrian squadron anyway.
The aim was primarily to defeat the Danish navy, secondary to lift the blocade of the German ports.
To counter them was a part of the Danish navy, consiting of the larger ocean going ships. Two hyper modern steam screw frigates, Niels Juel and Jylland, supported by a just as modern corvette, Heimdal.
In May 1864 the two squadrons closed in on each other at Helgoland. The number of islands close to the mouth of river Elbe in present day Germany.
Britain was not pleased about having an Austrian squadron sailing around in th North Sea and a British patrolship, Aurora, informed the Danish fleet.
And on the 9. May the two squadrons formed line of battle.
It became a slogging match, both sides pounding away on each other, however the Austrian ships had no support in their Preussian allies. The canon boats, perhaps wisely, chose to stay out of range.
By mid afternoon, the Austrian ships had suffered hard and the two ships strayed into British waters. (At that time Britain posessed a number of islands in the island chain, going from Denmark, across Germany to the Netherlands.) And the British patrolship, Aurora, sailed in between the two squadrons. Ending the battle.
Now, those of you well versed in geography will ask: what on earth that has got to do with Norway, hundreds of kilometres away.
While the two squadrons licked their wounds and prepared to fight again the next day, orders came in that there had been a ceasefire. And since Jutland at that time had been occupied by German troops and there was no harbour bigh enough along the west coast anyway, the Danish squadron was ordered to sail to Kristianssand in Norway and off load the wounded and then proceed to Copenhagen.
So Danish sailors ended up being treated and buried in Norway and that's why Mary is in Norway.
The casualties were:
Danish: fourteen dead, 53 wounded.
Austrian: 32 dead, 59 wounded.
Here is a painting of the battle from the frigate Niels Juel: https://app.box.com/s/sdxnysx7c1pt9z9925rk
As you can see the modern name for the command center on a ship, bridge, stems from this period.
The captain and officers really stood on a bridge.