It consisted originally of the 4th, 8th, and 12th divisions which were mobilized in South-Eastern Finland in the vicinity of Hamina, Suur-Miehikkälä, Anjala and Luumäki.

[3] The corps was initially tasked with defending an area spanning from the Virolahti at the Gulf of Finland to Kuurmanpohja near Joutseno.

[5] On 28 June, a few days before taking command of the 10th Division, the IV Corps was given orders to plan for an offensive.

[7] Indeed, following the Soviet 23rd Army's withdrawal from Vyborg,[8] parts of IV Corps began to pursue them towards the pre-Winter War border.

[12] Other sources state that the combat actions south of Vyborg resulted in a total of 9000 Soviet prisoners of war and 7000 dead left in the area, while the Finns suffered approximately 3000 casualties.

[16] On 15 October 1941, the IV Corps consisted of the 12th, 2nd, 18th and 19th Divisions positioned on the western half of the Karelian Isthmus.

These efforts began in the IV Corps in October, resulting in the demobilization of 4549 men by end of November.

[24] Consisting initially of only the 2nd and 18th Divisions, the Cavalry Brigade, and Coastal Artillery Regiment 2,[25] the reformed IV Corps was hit by the spearhead of the Soviet Vyborg–Petrozavodsk offensive on 10 June 1944.

However, the situation was complicated by the concurrent Soviet demands that the Finns remove the German forces remaining in northern Finland.

As a result of disagreements regarding the strength and composition of the post-war Finnish army, the plan had not been approved by the start of November.

This was of significant concern for the Finns, as time was running out for completing the demobilization by the original 5 December deadline while the Lapland War, the removal of remaining German forced from northern Finland, continued.