The Swedes crossed the border in several brigades, of which the General-in-chief, Gustaf Mauritz Armfelt, followed the first; he arrived at the strong Norwegian position at Lier and decided to attack it, to reach Kongsvinger Fortress.

Armfelt did not follow up his victory, instead remaining at Lier until late May, when he received orders to withdraw; the Swedes retreated out of Norway in May–June, after a fruitless campaign.

[3] In mid-April, the Swedish forces went on the counter-offensive with the goal of capturing Norway,[6] as compensation for a potential loss of the eastern territorium (Finland).

[9][10] Werner Nicolai de Seue, the commander of the Norwegian forces, had a total of between 1,700 and 2,400 men at his disposal towards Kongsvinger Fortress, including the garrison.

[11][12] On the 17th, the Swedish vanguard reached Lier, where the Norwegians had entrenched themselves in a very advantageous position which blocked the path to the fortress, 5 km (3 mi) to the north.

[16] At 08:30, the left Swedish division of 200 men (mainly from the Värmland Jäger Regiment), under Matern, drove back the Norwegian light infantry south of the entrenchments, towards the direction of the redoubt.

However, Lilljeström's attack over Tarven had failed while Belfrage had been repelled east of the redoubt, which convinced Armfelt to cancel a continued assault and order a retreat.

[20][21] Near 18:00, as the Norwegians could be seen shifting their troops, the Uppland Regiment, under major Hård, seized the initiative and stormed the redoubt under the cover of a gun—it was taken after a hard-fought melee.

[26] On 24 May, six days after the Battle of Mobekk, Armfelt received orders from Gustav IV Adolf to act defensively, as the king planned an attack on Denmark.