The Battle at Herdaler was a battle between the Norse Viking leader Olav Haraldsson (later King of Norway) and Finnish people at Herdaler in Finland around years 1007/8. The Saga of Olaf Haraldson

Heimskringla

Heimskringla is the best known of the Old Norse kings' sagas. It was written in Old Norse in Iceland by the poet and historian Snorri Sturluson ca. 1230...

 tells how Olav Haraldsson (Olaf II of Norway, also Saint Olaf), the King of Norway, plundered in Finland and almost got killed in the battle.

After this they sailed to Finland and plundered there, and went

up the country. All the people fled to the forest, and they had

emptied their houses of all household goods. The king went far

up the country, and through some woods, and came to some

dwellings in a valley called Herdaler, -- where, however, they

made but small booty, and saw no people; and as it was getting

late in the day, the king turned back to his ships. Now when

they came into the woods again people rushed upon them from all

quarters, and made a severe attack. The king told his men to

cover themselves with their shields, but before they got out of

the woods he lost many people, and many were wounded; but at

last, late in the evening, he got to the ships. The Finlanders

conjured up in the night, by their witchcraft, a dreadful storm

and bad weather on the sea; but the king ordered the anchors to

be weighed and sail hoisted, and beat off all night to the

outside of the land. The king's luck prevailed more than the

Finlanders' witchcraft; for he had the luck to beat round the

Balagard's side in the night. and so got out to sea. But the

Finnish army proceeded on land, making the same progress as the

king made with his ships. So says Sigvat: --



"The third fight was at Herdaler, where

The men of Finland met in war

The hero of the royal race,

With ringing sword-blades face to face.

Off Balagard's shore the waves

Ran hollow; but the sea-king saves

His hard-pressed ship, and gains the lee

Of the east coast through the wild sea."

The location of "Herdaler" in Finland is not certain. The expedition's possible place could have been north of Uusimaa

Uusimaa

Uusimaa, or Nyland in Swedish, is a region in Finland. It borders the regions Finland Proper, Tavastia Proper, Päijänne Tavastia and Kymenlaakso...

 in Hirdal in the present-day town of Ingå

Ingå

Ingå is a municipality of Finland.It is located in the province of Southern Finland and is part of the Uusimaa region. The municipality has a population of and covers an area of of which is water...

. That makes it the first mentioning of a place located in present-day Finland in historical literature. It has been suggested that based on the similarity of names "Herdaler" and "Balagard" to names Härjedalen

Härjedalen

' is a historical province or landskap in the centre of Sweden. It borders the country of Norway as well as the provinces of Dalarna, Hälsingland, Medelpad, and Jämtland...

 and Dalagård, the king's expedition would have actually taken place in Dal River

Dal River

The Dal River is a river in central Sweden that flows from the north of Dalarna and runs into the sea in northern Uppland; it is commonly considered to be the southern border of Norrland. The northern part is split into two rivers: Österdalälven and Västerdalälven. The two connect in Djurås...

 area in Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

. For one reason or another, Olaf's plundering in Sweden would have been relocated to Finland, although this is speculation.