'Kilpapurjehdus' was the Finnish operation to remilitarise the Åland islands group in the mouth of the Gulf of Bothnia between Finland and Sweden, and thus dominating the mouth of the Gulf of Finland between Finland and Soviet-occupied Estonia, at the beginning of the 'Jatkosota' (22 June/late June 1941).

The implementation of the Moscow treaty of 1940, which had ended the Soviet/Finnish 'Talvisota' (Winter War) of 1939/40, created significant strategic problems for Finland. The forced return of evacuated machinery, locomotives and rolling stock, and the Soviet intransigence on matters such as fishing rights and the use of the canal linking Lake Saimaa with the sea, which could have eased the hardship attendant on Finland’s loss of Karelia and the area immediately to the north of Lake Ladoga, increased Finland’s already considerable distrust of Soviet longer-term objectives in the region.

The situation was further exacerbated by the behaviour of the new Soviet ambassador to Helsinki, who was singularly undiplomatic, attempted to further Soviet interests in Finland, and in his reports constantly recommended the conquest and annexation of Finland.

On 23 June the USSR demanded mining rights in Petsamo on Finland’s short north coast between the USSR and Norway, and the site of strategically important nickel ore deposits. Four days later the USSR also demanded the demilitarisation of the Åland islands group and, following Sweden’s signature of a troop transfer agreement with Germany on 8 July, demanded similar rights for Soviet troop transit to Hanko, the Soviet treaty base at the tip of the peninsula on the Finnish side of the Gulf of Finland’s mouth. The Finns agreed to these transfer rights on 6 September, and to the demilitarisation of the Åland islands on 11 October, but the negotiations on mining rights at Petsamo continued.

The USSR also demanded changes in Finnish internal politics including, for example, the removal of a cabinet member. This whole process was altogether too reminiscent of the process by which the USSR had paved the way for the occupation and annexation of the Baltic republics, on the other side of the Gulf of Finland, only a few months earlier.

By this time, but unknown to Finland, the Germans had started to plan their 'Barbarossa' invasion of the USSR, and whereas he had expressed no interest in Finland before the 'Talvisota', Adolf Hitler had by now appreciated the fact that Finland was an excellent base for operations against the northern USSR. In the first weeks of August, increased German fears of a Soviet attack on Finland caused Hitler to lift the embargo of German arms to Finland, and negotiations were launched to open the way for German troop transfer rights in Finland in exchange for arms and other matériel. This was a German breach of the Molotov-Ribbentrop Pact of August 1939, as well as Finnish breach of the Moscow treaty. However, Soviet negotiators had insisted that the troop transfer agreement to Hanko should not be published, and this facilitated the Finnish secrecy about a troop transfer agreement with the Germans, at least until the first German troops started to cross Finnish soil.

The negotiations about Petsamo were still continuing when, in January 1941, the Soviets demanded that the negotiations be concluded without further delay and, on the same day, terminated grain deliveries to Finland. The Soviet ambassador was recalled on 18 January and the Soviets started radio broadcasts of an anti-Finnish nature.

The German forces in northern Norway reported early in February that the USSR had concentrated in Murmansk, just to the east of Petsamo, a force of 500 fishing vessels, sufficient for the transport of a single division along the coast. Hitler ordered troops in Norway to undertake the immediate occupation of Petsamo in 'Rentier' should the USSR attack Finland.

After the failure of the nickel negotiations, diplomatic activities came to a halt for a few months, but during the same period there arrived a greater German interest in Finland. On 5 May the German foreign ministry sent a representative to Finland to clarify that war between Germany and the USSR would not be launched before spring 1942. The Finnish leadership believed this 'fact', at least officially, and forwarded the message to the Swedes and the British. When the war broke out in the following month, it was understandable that both Swedish and British governments felt that the Finns had lied to them.

In the spring of 1941 joint operational plans had been discussed with Germany, as well as other military aspects of a war with the USSR, such as communications and the security of sea lanes. Finland made major requests for matériel aid, and said that she was prepared to join Germany in a war against the USSR with some prerequisites: a guarantee of Finnish independence, the re-establishment of the borders of the period before the 'Talvisota', continued grain deliveries, and no crossing of the border with the USSR before a Soviet incursion.

The first German forces for the extreme north of 'Barbarossa' arrived in Petsamo on 7 June. The Finnish parliament was informed of these matters only on 9 June, when the first mobilisation orders were issued for the troops needed to safeguard the imminent general mobilisation. On 20 June the Finnish government ordered the evacuation of 45,000 persons living along the border with the USSR. On 21 June Jalkaväenkenraali Axel Erik Heinrichs, the chief of the Finnish general staff, was told by his German counterpart that 'Barbarossa' was about to begin. The offensive had already started in the northern Baltic by the late hours of 21 June, when German minelayers, previously concealed in the Finnish archipelago, laid two large minefields across the Gulf of Finland. These minefields were sufficient to confine the Soviets' Baltic Fleet easternmost part of the Gulf of Finland. Later in the same night, German bombers flew along the Gulf of Finland to Leningrad, where they mined the harbour and the Neva river. On the return trip, the bombers refuelled at the Finns' Utti airfield.

Fearing that the Soviets would attempt to occupy the Åland islands from their base at Hanko, or from the ports they had in occupied Estonia, the Finns launched the 'Kilpapurjehdus' operation in the early hours of 22 June to reoccupy and remilitarise the Åland islands. Soviet bombers attacked the Finnish ships during the operation, but inflicted no damage. At much the same time Finnish submarines also laid six small minefields between Suursaari (Suur island) in the Gulf of Finland and the Estonian coast, as agreed by Finland’s pre-war defensive agreement with Estonia. Thus was Finland committed to the 'Jatkosota' (1941/44).