Ah-ah-ah-ah,
This is a bit inconsequential, but I liken this to the "cry of the Berserkrgangr" if you will. A broader definition could be taken as the "cry of the Viking warrior" even.
We come from the land of the ice and snow,
From the midnight sun where the hot springs blow.
Maybe this was inspired by Led Zepplin's tour of Iceland, but Iceland isn't the only "land of the ice and snow". Greenland, Scandinavia, Denmark, even the north of Scotland, are lands of ice and snow. The "midnight sun" and "hot springs" are found in some parts of Scandinavia also. Due to other reasons I shall detail below, I believe this particular land of ice and snow is Scandinavia.
The hammer of the gods,
This is a reference to mjolnir, Thor's hammer. For all of those who aren't too versed with Viking religion, this belongs to the norse pantheon of Gods, otherwise known as Asatru or Norse Heathenism./p>
Will drive our ships to new lands,
To fight the horde, singing and crying:
Around 8th Century AD, the Norse tribes began to suffer harsher and harsher winters, and many began to starve. Many began setting out in their longboats, searching for new lands, ready to fight any in their way to take back food to their hungry people.
Valhalla, I am coming!
Another religious reference, and again an Asatru religious reference. To ascend to Valhalla, one had to fight with valour and honour.
On we sweep with threshing oar,
Our only goal will be the western shore.
In 789 A.D. a lone longship gets lost at sea and washes up on the shores of Britain. Confused and lost, the crew do a short reconnaisance of the area, then after gathering their bearings, return home to Scandinavia. Thus, it makes sense that this land is Scandinavia and not Iceland.
How soft your fields so green,
Can whisper tales of gore,
The tale of "how soft your fields so green", the luscious, rich and fertile lands of the British, brought the entire Viking fleet in 793 A.D. They swept onwards, their only goal was the western shore, and they first attacked Northumbria, invading the island of Lindisfarne, sacking the monastery of St. Cuthbert and making off with the gold. After this, tales of the brutality and verocity of the Vikings spread throughout, the British "can whisper tales of gore" as the story of the murdered monks spread.
Of how we calmed the tides of war.
We are your overlords.
At the time the Vikings invaded, Britain was divided into three kingdoms; Northumbria, Mercia and Wessex. They were constantly at war, territorial conflicts were a common occurence, and each kingdom wanted to be the only kingdom. In 865 A.D. the Viking raids ended, and the Norsemen and the Danes backed the Vikings by sending over their combined forces. They landed in East Anglia, and by 875 A.D. Mercia and Northumbria had submitted to their might. At this stage, the Vikings were the "overlords" of much of Britain, and a great portion of it experienced lasting peace for the first time in hundreds of years. Thus, the Vikings had "calmed the tides of war".
So now you'd better stop and rebuild all your ruins,
For peace and trust can win the day,
Despite of all your losing.
Although the Vikings dominated most of Britain, Wessex had not fallen, and independent lands, such as Wales, still stood. The Vikings would soon lose their grip on the lands, and the British would "stop and rebuild", making up their losses, and band together, "for peace and trust can win the day". | 
