Juuso Walden was appointed new Managing Director of United Paper Mills Ltd in spring 1940. Jämsänkoski had appointed a new Superintendent the year before, the Technical Director of the pulp mill, Lauri Tiilikka. Both the Managing Director and the Jämsänkoski Superintendent took up their posts at a difficult time. Staff returning from the front had to be placed into jobs, and production that had been reduced during the Winter War raised back to normal.

Due to fuel shortages, the Jämsänkoski pulp mill stood idle on several occasions in 1940 - 1942. During the Continuation War, pulp was only produced for the company's own paper mill, and paper manufacture reached almost peace time levels. Demand for paper was affected by the reduced output around the world, due to the war. Thus, the price of paper also rose. Exports to England ended in 1940, and the following year also to the United States and South America. Exports were focused on Germany and the countries under its occupation. As the war went on, the importance of Germany increased further, as essential imported goods were also obtained from there. The years 1942 - 1943 were financially good for the company, and dividends of 8 -13 percent were issued.

Jämsänkoski pulp mill built its own pyrite plant, so that domestic sulphur pyrites could be used. Another plant completed in wartime was the spirit factory, manufacturing sulphite spirit for use as fuel. The factory only operated for a short period towards the end of the war. Exercise books and note pads were printed in the Jämsänkoski paper mill processing section, which reached peak production during the war.


After the war, old trade links with Western Europe were re-established, and the exports to the Soviet Union also started to consist of goods other than war reparation products. Demand for paper in global markets exceeded supply. There was a brief recession towards the end of the 1940s, and paper output at Jämsänkoski was reduced by a third. The start of the 1950s was a boom period caused by the war in Korea, and record quantities of paper were sold.

In Jämsänkoski, the post-war years were a period of brisk building. A new sawmill rose at Olkkola in Jämsä in 1946. Residential buildings went up in the town centre and single-family housing areas. The mills were connected to the national power grid in 1949, and a railway was finally built to Jämsänkoski in 1951. The Myllykoski mills separated from United Paper Mills Ltd in 1952. Thus, the parent company was left without a newsprint mill.


Building of the newsprint mill in Kaipola had been part of Juuso Walden's plan even before the company was finally split up. The construction work began in 1952, and the first papermaking machine was turned on in 1954. A second papermaking machine followed two years later. In addition, PK 3 was brought from the Simpele mill to manufacture wrapping and tube paper. Jämsänkoski's PK 3 in turn started up in 1960. Alongside the new papermaking machine, capacity of the pulp mill was also adjusted to correspond to the increased demand for pulp. Most of the exports of Jämsänkoski and Kaipola paper went to West Germany, Great Britain and the Soviet Union.

Increased international competition in the paper markets and extensions at Kaipola brought the company financial difficulties. The Kaipola mills' losses pushed the result of the whole United into the red in 1964 -1967. Even sale of the manufacturing unit was on the cards at the end of the decade. The company’s foreign business interests were also making losses.

Honorary Mining Counsellor Juuso Walden lost the confidence of the principal financing bank, KOP, and a holding company took a third of United shares. Walden was pensioned off at the end of 1969. The new CEO from the beginning of 1970 was Niilo Hakkarainen, B.Sc. (Eng.). It was down to him to build United up into a profitable company once more.