Battle of Lahti was a 1918 Finnish Civil War battle, fought from 19 April to 1 May between the German troops and Finnish Whites against the Finnish Reds in Lahti, Finland. Together with the Battle of Viipuri, from 24 to 29 April, it was the last major battle of the war.
The German unit Detachment Brandenstein, commanded by colonel Otto von Brandenstein, attacked Lahti on 19 April, taking the town by the next evening. At the same time, a column of tens of thousands of Red refugees was approaching Lahti from the west. On 22 April, the Reds launched a counterattack in order to break through the German lines and clear the way for the fleeing people. The attempt failed and the Reds finally surrendered on 1 May. As a result, the Whites and Germans captured about 30,000 Reds and their family members who were placed to a concentration camp in the outskirts of Lahti.
Background
At the time of the Finnish Civil War, Lahti had a population of 6,500. The town was important for the Reds due to its location by the vital Riihimäki–Saint Petersburg railway, connecting Lahti to the major war theatres in Tavastia and Karelia. Red troops were formed and trained in the Hennala Garrison which the Russians had built in the early 1910s. As the Red front had collapsed in the northern part of Tavastia and the Battle of Tampere was over in 6 April, tens of thousands of Red refugees headed east through Hämeenlinna and Lahti. In the late April, there were about 40,000 Reds inside the triangle formed by the towns of Hämeenlinna, Riihimäki and Lahti.
The German Baltic Sea Division landed in Hanko on 3 April. After the victorious Battle of Helsinki, fought 12–13 April, the division marched north to Riihimäki and Hämeenlinna, which forced the Red refugees to head to Lahti. Another German unit, Detachment Brandenstein, landed 75 kilometres east of Helsinki in Loviisa 12 April. The original plan for Detachment Brandenstein was to attack the Red stronghold of Kotka and then cut the Saint Petersburg railway in Kouvola. For some reason, the Germans finally decided to move north to Lahti, instead of Kotka in the east.
German offensive
As the Germans reached Lahti along the Loviisa–Vesijärvi railway, the Reds started building trenches, artillery batteries and other defensive posts to the slopes of the Salpausselkä ridge. In 13 April, the Detachment Brandenstein took the Orimattila village 20 kilometres south of Lahti. The offensive against the town was launched six days later on 19 April at 5 am. The main force commanded by the lieutenant colonel von Luck took the village of Villähde, 9 kilometres east of Lahti, at 1:00 pm and cut the Saint Petersburg railway, while the second unit attacked Lahti and reached the Railway Station at 7:00 am without any resistance. After taking the Hennala Garrison, the Germans entered the town in the evening. Colonel Luck and his men headed for the General Hospital at 10:00 pm and most of Lahti was held by the Germans by 11:00 pm. All this happened with hardly any resistance by the surprised Reds. Instead of the town itself, the Reds were only defending their positions in the Salpausselkä ridge. It is unclear why the attack took the Reds by surprise, as they knew the Germans were approaching. One explanation is their poor reconnaissance and surveillance.
On the morning of 20 April, the Germans reached the harbour by the Vesijärvi lake. At the same time the Finnish White Army division, commanded by the Estonian major Hans Kalm, entered the town from north as the Reds on the Radiomäki hill had surrendered. The German commander colonel Otto von Brandenstein and Hans Kalm greeted each other in a modest ceremony held in the Lahti main street. On the next day, a small clash occurred as a group of 1,000 Red Guard fighters came by armoured train to Okeroinen, a village in Hollola, 5 kilometres south of Lahti. The Reds tried to break into the town but were pushed back. During the first two days of the battle, the Germans lost six men killed. Red losses were at least 37 killed and 500 captured. 300 more were captured within next three days as the Germans searched for Reds in their homes. The ones found with a fired rifle were shot.