The black day of the Finnish Army was 10 June 1944. After a massive artillery and air preparation accompanied by probing attacks on 9 June, the Soviet Twenty-first Army on the morning of the 10th concentrated the full force of its attack on the left-flank division of the Finnish IV Corps holding the western side of the front on the Isthmus of Karelia. In a massive assault three Russian divisions annihilated one regiment of the Finnish division, and before noon the Russians had broken through the Finnish front to a distance of approximately six miles.
Although there had been advance warnings the Russian offensive took the Finnish High Command by surprise. During May there had been indications of an attack in the making, and on 1 June Finnish Army Intelligence warned that an offensive was to be expected within ten days. Four or five days before the attack the Russians began radio silence-an almost infallible sign. But the Army operations chief was not convinced, and his judgment carried the greatest weight with Mannerheim.
When the attack began the III Corps held the left and the IV Corps the right flank of the Finnish front on the Isthmus. Together they had three divisions in the line and one brigade in reserve. In the second line stood another three divisions plus one brigade engaged in constructing fortifications. Lastly, the Finnish Armored Division was stationed east of Vyborg. On the Isthmus the Finns had three defense lines. The first of them, the front, roughly followed the old Finnish Soviet border. The second, immediately to the rear, laid out in terrain militarily more advantageous than the first, ran in an almost straight line across the Isthmus from Vammelsuu on the Gulf of Finland to Taipale on Lake Ladoga. The third ran from Vyborg to Kuparsaari and thence along the north bank of the Vouksi River to Taipale. It had strong natural advantages but had not been placed under contstruction until November 1943 and was far from completion.” Between the third Isthmus line and the heart of Finland there was the so-called Moscow Line along the 1940 border. It had some concrete fortifications, and additional construction was in progress, but it had no natural advantages and could only be used for a last-ditch stand.
Concerning the Finns’ capacity for resistance the Germans had had severe doubts at least since early 1943. In June 1943 German General Dietl repeated his prediction made in February of that year that the Finnish Army would not be able to withstand a strong Soviet attack. The Finns, he stated, were superior to the Germans as forest fighters and in dealing with adverse conditions of terrain and climate, but they preferred to avoid pitched battles.19 In July 1944, after the Russian summer offensive had passed its peak, an OKW observer concluded that the Finnish setbacks could be blamed, at least in part, on lack of training and neglect of fortifications. He also believed that in June 1944 the Finns had no longer expected a Russian attack and that, until the shock of the breakthrough on 10 June produced a more realistic judgment, they had a tendency, induced by their experiences in the Winter War and 1941, to underestimate the enemy. This last criticism was one from which the Germans extracted a degree of wry satisfaction since they had long felt that the Finns failed to appreciate fully the nature of Germany’s problems on the Eastern Front. There was also a feeling that the Finns had failed to adapt to the conditions of total war-the near-peacetime conditions prevailing on the home front were frequently cited-and were trying to get through the war with as little inconvenience to themselves as possible.
To achieve and exploit their breakthrough the Russians had assembled 10 rifle divisions and the approximate equivalent of 3 tank divisions in addition to the 3 static divisions already in the front on the Isthmus of Karelia. In the assault area their artillery reportedly numbered 300 to 400 guns per kilometer of front. For striking power the Soviet command relied almost exclusively on its tremendous superiority in tanks, artillery, and aircraft. The rifle divisions were weak, averaging about 6,200 men each, and their will to fight declined rapidly after the first few days of combat. The Russian tactics, concentration on a narrow front with a tremendous commitment of materiel and-following the breakthrough-exploitation by several corps abreast, followed a pattern which the German armies on the Eastern Front had come to regard as standard.
Immediately after the Russian breakthrough on 10 June it was clear that the IV Corps could not hold in front of the second line. Mannerheim gave the IV Corps a division from the reserve, a regiment of the III Corps, ordered the Armored Division to move up from Vyborg, and set in motion the transfer of one division from East Karelia and recall of the 3d Brigade from the Twentieth Mountain Army. By the 12th the IV Corps had withdrawn to the second line. The III Corps, which had not been under attack, was then also ordered back. On the same day Mannerheim ordered a division and a brigade out of East Karelia to the Isthmus and asked the OKW to release the weapons and grain which had been intended for Finland but were held in Germany by Hitler’s embargo. On the following day Hitler agreed.
Its chances of holding the second line slim, the Finnish High Command was forced to consider radical measures. On 13 June Finnish General Heinrichs told Dietl that, if the second line were lost, the Finnish intention was to give up the Svir and Maaselka fronts and pull back in East Karelia to a short line northeast of Lake Ladoga, thus freeing two to three additional divisions for the Isthmus. Since November 1943 work had been in progress on the so-called U-Line, the line of the Uksu River-Loimola Lake-Tolva Lake. Dietl urged the Finns to carry out that intention, but he feared that out of reluctance to give up East Karelia they would hesitate too long.
Later he recommended to Hitler that German policy be to tie the Finns to Germany by giving them as much support as possible and to hold them to complete operational measures, not allowing them to dissipate their strength in attempts to hang on in East Karelia. On the shorter line, he thought, Finland might hold out indefinitely, which would assure preservation of Finland and, at the same time, spare the Twentieth Mountain Army the necessity of executing Operation BIRKE.
While Dietl was at Mikkeli the second line on the Isthmus was already under attack. It held for a day; but on 14 June the Russians brought up their heavy weapons and, since-as a captured map later revealed they had reconnoitered the second line in detail before the offensive began, were able to attack in force immediately. Overwhelming the Finns a second time with the weight of their artillery fire and tanks, they broke through the second line at the village of Kutersel’ka and by 15 June had smashed the Finnish front on an eight-mile stretch from Kutersel’ka to the coast. By then it was apparent that the Russians’ main effort would be directed along the railroad line to Vyborg. The Finns had virtually no hope of stopping them short of the city and were worried by the danger that they could reach and close the seventeen mile-wide narrows between Vyborg and the Vuoksi River before III and IV Corps could be withdrawn. Such a maneuver would in all probability be decisive, for it would end all hopes of holding the VyborgVuoksi line and would force the III and IV Corps to withdraw northward across the Vuoksi and, because there was only one bridge across the river, abandon much of their heavy equipment on the way.
On 16 June Mannerheim ordered the withdrawal to the VyborgVuoksi Line. On the 20th, after four more days of heavy fighting, the IV Corps, under continuing Russian pressure, moved into the line between Vyborg and the river while the III Corps established itself on the north bank of the Vuoksi and held a bridgehead on the south bank across from Vuosalmi. Once again the Finnish Army stood on the line where it had stopped the Russians in 1940. The withdrawal had gone better than might have been expected, chiefly because the Russians, rigidly intent on the city of Vyborg, failed to strike toward the VyborgVuoksi narrows. But the Finns still had no cause for optimism. The Russian forces on the Isthmus had been gradually increased to 20 rifle divisions, 4 tank brigades, 5 to 6 tank regiments, and 4 self-propelled assault gun regiments. Against these the Finns, drawing on the last units which could be spared from East Karelia, could assemble no more than 10 divisions and 4 brigades.
Political Developments and German Aid
The military crisis resulting from loss of the second line on the Isthmus inevitably brought a political crisis in its wake. On 18 June the Finnish Cabinet held a long meeting. Concerning its results the German Minister could only secure evasive answers. On the evening of the 19th Heinrichs asked Erfurth whether Germany was willing to provide aid other than weapons, specifically six divisions to take over the front in East Karelia and release Finnish troops for the Isthmus. Mannerheim repeated this request on the following day. At about the same time the Finns reestablished contact with the Soviet Government.
In Germany the necessity for extending help to Finland had already been recognized and accepted even though the Germans themselves faced a dangerous situation in Normandy and expected the greatest Soviet offensive of the war to break loose any day. Hitler lifted the embargo on shipments to Finland on 13 June, and on the 19th torpedo boats delivered 9,000 Panzerfaust (antitank grenades). Three days later 5,000 Panzerschreck (bazookas) were airlifted to Finland. To give the six divisions Mannerheim requested was impossible, but on the 20th the OKW informed him that Germany was ready to give every kind of help if the Finnish Army was actually determined to hold the Vyborg-Vuoksi Line. Aside from weapons and supplies, the Germans offered the 122d Infantry Division, a self-propelled assault gun brigade (the 303d), and air units consisting of a fighter group and a ground attack close support group (Stukas) plus one squadron. The ground troops were drawn from the Army Group North and the air units from the Fifth Air Force in Finland and the First Air Force with the Army Group North. The aircraft were transferred immediately and on 21 June flew 940 support missions for the Finnish Army.
Although the German aid was offered and, in part, delivered without a prior commitment on Finland’s part, its price was well known to both parties. On 21 June President Mannerheim informed Hitler that Finland was prepared to establish closer ties with Germany, and on the following day Ribbentrop flew to Helsinki to conduct the negotiations in person. That the Foreign Minister himself undertook the mission indicated a determination to bind Finland to Germany unequivocally. For this reason his unannounced appearance in Finland, aside from being a surprise, aroused dismay in the Finnish Government.
The negotiations, which Ribbentrop conducted in the high-pressure manner for which he was noted, did not go smoothly. Both sides recognized that in view of the strong sentiment for peace, which had already resulted in a movement to bring to power a government under Paasikivi, the Finns could not give a declaration which had to be ratified by Parliament. The Germans offered to compromise and accepted a declaration signed by the President. On 23 June the German position was strengthened when the Soviet Government informed the Finns that it would not open negotiations until the President and Foreign Minister declared in writing that Finland was ready to capitulate and turned to the Soviet Union with an appeal for peace. On the 24th Ryti and Ramsay conferred with Mannerheim at Mikkeli, and on the next day Hitler added pressure with a directive which stated categorically that a public clarification of Finland’s attitude was to be secured. If such a clarification could not be achieved, support for Finland would stop. Late on the night of 26 June Ryti called in Ribbentrop and handed him a letter in which he stated that he, as President of Finland, would not make peace with the Soviet Union without the consent of the German Government and that he would not permit any government appointed by him or any other persons to conduct armistice or peace talks or negotiations serving those purposes without German consent.
Ribbentrop returned to Germany in triumph, but with a contract which was unenforceable by any means at Germany’s command. The end result of his mission was to obscure the obvious generosity of German aid extended at a time when it could scarcely be spared and to arouse, instead, in the minds of the Finns a feeling that they had been made victims of blackmail in their hour of greatest need. While this cannot be said to have affected materially future Finnish actions, it went far toward relieving any moral qualms they might have had concerning the course they were about to pursue.
Within a week after the Ryti letter was signed the United States broke off diplomatic relations with Finland. The Finnish Minister in Washington and his principal aides had already been handed their passports and ordered out of the country in June. Although this was a severe blow, the fact that a declaration of war did not follow could, in the long run, be regarded as a major accomplishment of Finnish diplomacy: Finland had weathered the war without an irrevocable break in its ties with the democracies.
The oppressive atmosphere surrounding the June negotiations was deepened by Dietl’s death on 23 June. He had conferred with Hitler on the previous day and was returning to Finland when his plane crashed in the Austrian Alps. The accident was kept secret for several days for fear of its effect on the negotiations. On 28 June Generaloberst Lothar Rendulic took command of the Twentieth Mountain Army. For the Finns the June negotiations had one purpose-to secure assistance in stopping the Russian offensive. The Ryti letter achieved that purpose, but the aid that came was less than the Finns expected.
It was in fact less than the Germans had intended to give, for, in the meantime, the massive Russian offensive against the Army Group Center which began on 22 June had imposed a nearly overwhelming drain on German resources. The 303d Self-propelled Assault Gun Brigade reached Finland on 23 June, and the 122d Infantry Division arrived five days later. But a second assault gun brigade intended for Finland had to be diverted to the Army Group Center at the last minute, and a corps headquarters to command the German units in Finland, although pulled out of the southern sector of the Eastern Front, was never sent. German weapons and supplies, including some tanks and heavy equipment, continued to flow to Finland. The Panzerfaust and Panzerschreck, once they had been proved effective, greatly increased the Finns’ ability to withstand Russian tank attacks and played a major role in restoring the confidence of the Finnish Army.