During her first years Ilmarinen made a few journeys to different ports in Finland, once running aground near Vaasa.

When the Winter War erupted, Ilmarinen and her sister ship Väinämöinen were dispatched to the Åland Islands in order to guard against a possible invasion.
Due to a decree by the League of Nations, the Ålands were to be demilitarized in peacetime.
The Finnish Navy was to transfer resources there when conflict arose.

The threat against the Åland Islands receded after thick sheet-ice began covering the Baltic Sea in December 1939.
The two coastal defence ships sailed to Turku where they provided anti-aircraft support for the city.
They were painted white to prevent Soviet bomber crews from spotting them, but were targeted by aircraft on several occasions, resulting in one death and several injuries.

During the Continuation War the two ships shelled the Soviet base at Hanko Peninsula on five occasions in July–November 1941.
Ilmarinen fired twenty shells at the Soviet airfield at Täcktom on 12 July 1941.
The airfield had previously been bombed by German Junkers Ju 88s of Küstenfliegergruppe 806.

The two Finnish coastal defence ship participated in Operation Nordwind on 13 September 1941, in which German forces were to take the Estonian islands of Saaremaa and Hiiumaa.
A group of Finnish and German ships were to be used in a diversionary operation to lure the Soviet fleet into battle – away from the real invasion force coming up from the south.
Another German fleet, including the cruisers Emden, Köln, and Leipzig, waited further away to join the battle if the Soviets turned up; however, the northern fleet remained unnoticed and an order was given to turn around when they had reached a point some 25 nautical miles (46 km; 29 mi) south of Utö.
The formation was led by minesweepers, but some mines had escaped being swept.
The crew of Ilmarinen failed to take proper notice of the dragging paravane cable.
It is likely that the ship had caught one or two sea mines in the paravane, and when the ship turned, the mines struck the bottom of the hull and exploded.
The explosion blew a large hole in the ship, which soon developed a strong list and keeled over.
The ship sank in just seven minutes.
Only 132 men of the crew survived, and 271 were lost, most of them trapped inside the hull.
Fifty-seven were rescued by the patrol boat VMV 1, which had maneuvered to the capsized hull and took on as many of Ilmarinen's crew as she could.
During this time she too was at great risk of being obliterated if Ilmarinen's magazines had ignited.

The survivors were later known as Ilmarisen uimaseura (Ilmarinen's Swimming Team).
Among the survivors were Ilmarinen's captain, Commander Ragnar Göransson, and the Commander of the Finnish Navy, Commodore Eero Rahola, as well as Lieutenant Viljo Revell, later a renowned architect.

The loss of Ilmarinen is the greatest single loss of the Finnish Navy to date.
The military command tried to keep the loss secret, but Swedish newspapers soon reported the incident, and the numerous sailor obituaries in Finnish newspapers could also have alerted the Soviets, who soon also reported the loss.

The ship was located in 1990.
It was found upside-down, deeply embedded in mud, resting at a depth of 70 metres (230 ft).
It is classified as a war grave.
The wreck of Estonia is some 15 km (9.3 mi) away.
During her first years Ilmarinen made a few journeys to different ports in Finland, once running aground near Vaasa.
When the Winter War erupted, Ilmarinen and her sister ship Väinämöinen were dispatched to the Åland Islands in order to guard against a possible invasion. Due to a decree by the League of Nations, the Ålands were to be demilitarized in peacetime. The Finnish Navy was to transfer resources there when conflict arose.
The threat against the Åland Islands receded after thick sheet-ice began covering the Baltic Sea in December 1939. The two coastal defence ships sailed to Turku where they provided anti-aircraft support for the city. They were painted white to prevent Soviet bomber crews from spotting them, but were targeted by aircraft on several occasions, resulting in one death and several injuries.
During the Continuation War the two ships shelled the Soviet base at Hanko Peninsula on five occasions in July–November 1941. Ilmarinen fired twenty shells at the Soviet airfield at Täcktom on 12 July 1941. The airfield had previously been bombed by German Junkers Ju 88s of Küstenfliegergruppe 806.
The two Finnish coastal defence ship participated in Operation Nordwind on 13 September 1941, in which German forces were to take the Estonian islands of Saaremaa and Hiiumaa. A group of Finnish and German ships were to be used in a diversionary operation to lure the Soviet fleet into battle – away from the real invasion force coming up from the south. Another German fleet, including the cruisers Emden, Köln, and Leipzig, waited further away to join the battle if the Soviets turned up; however, the northern fleet remained unnoticed and an order was given to turn around when they had reached a point some 25 nautical miles (46 km; 29 mi) south of Utö. The formation was led by minesweepers, but some mines had escaped being swept. The crew of Ilmarinen failed to take proper notice of the dragging paravane cable. It is likely that the ship had caught one or two sea mines in the paravane, and when the ship turned, the mines struck the bottom of the hull and exploded. The explosion blew a large hole in the ship, which soon developed a strong list and keeled over. The ship sank in just seven minutes. Only 132 men of the crew survived, and 271 were lost, most of them trapped inside the hull. Fifty-seven were rescued by the patrol boat VMV 1, which had maneuvered to the capsized hull and took on as many of Ilmarinen's crew as she could. During this time she too was at great risk of being obliterated if Ilmarinen's magazines had ignited.
The survivors were later known as Ilmarisen uimaseura (Ilmarinen's Swimming Team). Among the survivors were Ilmarinen's captain, Commander Ragnar Göransson, and the Commander of the Finnish Navy, Commodore Eero Rahola, as well as Lieutenant Viljo Revell, later a renowned architect.
The loss of Ilmarinen is the greatest single loss of the Finnish Navy to date. The military command tried to keep the loss secret, but Swedish newspapers soon reported the incident, and the numerous sailor obituaries in Finnish newspapers could also have alerted the Soviets, who soon also reported the loss.
The ship was located in 1990. It was found upside-down, deeply embedded in mud, resting at a depth of 70 metres (230 ft). It is classified as a war grave. The wreck of Estonia is some 15 km (9.3 mi) away.
Finnish coastal defence ship Ilmarinen