The ship, originally ordered in 1913 by the Russian navy under the name Maraviev Amurskyy, was launched in April 1914 at the Schichau-Werke shipyard in Danzig (now Gdańsk, Poland).

Pillau was assigned to the planned, final operation of the High Seas Fleet in the closing weeks of the war, but a large scale mutiny forced it to be canceled.

In the early years of World War II, she provided gunfire support to Italian troops in several engagements in the Mediterranean.

In 1912, the Imperial Russian Navy held a design competition for a new class of cruisers intended for service in their colonial empire, which were to replace the ageing Askold and Zhemchug in East Asian waters.

The Russian fleet was in dire need of new cruisers, and only Schichau promised to meet an early delivery deadline, so they received the contracts for two ships in December 1912.

These were to have been named Maraviev Amurskyy and Admiral Nevelskoy; the outbreak of World War I in July 1914 led to their seizure by the German government, and they became Pillau and Elbing, respectively.

Following the start of World War I, which saw Germany and Russia on opposite sides of the conflict, the German government seized the ship on 5 August, which was already nearing completion.

A significant detachment from the High Seas Fleet, including eight dreadnoughts and three battlecruisers, went into the Baltic to clear the Gulf of Riga of Russian naval forces.

[7] The year 1916 began with a similar pattern, though from 6 to 11 February, the commander of the fleet's torpedo-boats, Kommodore (Commodore) Johannes Hartog, temporarily used Pillau as his flagship.

During this period, Pillau led a patrol by the II, VII, and IX Torpedo-boat Flotillas to the western North Sea, which ended without combat.

On 21 April, Pillau joined a patrol led by the battlecruisers of I Scouting Group toward Horns Rev that ended the next day, again having failed to locate any hostile warships.

The flagship of II Scouting Group, the cruiser Graudenz, struck a mine during the operation; the acting commander, Kommodore Ludwig von Reuter, transferred to Pillau for the rest of the patrol.

[15] At around 18:30, Pillau and the rest of II Scouting Group encountered the cruiser HMS Chester; they opened fire and scored several hits on the ship.

The shell exploded below the ship's chart house; most of the blast went overboard, but the starboard air supply shaft vented part of the explosion into the second boiler room.

HMS Lion and Tiger both fired salvos at the ship before turning their attention to the battlecruiser SMS Derfflinger; Pillau's official record states that the British shooting was very inaccurate.

Pillau steamed ahead of Seydlitz to guide her back to Wilhelmshaven, but shortly after 10:00, the battlecruiser ran aground off Sylt.

After freeing Seydlitz at 10:30, the voyage back resumed, with a division of minesweepers steaming ahead testing the depth to prevent another grounding.

The raid resulted in the action of 19 August 1916, an inconclusive clash that left several ships on both sides damaged or sunk by submarines, but no direct fleet encounter.

The failure of the operation (coupled with the action of 19 August) convinced the German naval command to abandon its aggressive fleet strategy.

[22] On 5 November, Pillau sortied as part of the covering force, along with I and II Scouting Groups and III Battle Squadron for the rescue of the crew of the U-boat U-20, which had run aground on the Danish coast.

After a couple of hours in the town, the men returned to the ship and began to complete the tasks they had been ordered to do that morning as a show of good will.

They were tasked with replacing the heavy units of the fleet that had just completed Operation Albion, the conquest of the islands in the Gulf of Riga, along with the battleships of the I Battle Squadron.

The risk of mines that had come loose in a recent storm, however, prompted the naval command to cancel the mission, and Pillau and the rest of IV Scouting Group was ordered to return to the North Sea on 31 October.

On 17 November, the four cruisers of II Scouting Group, supported by the battleships Kaiser and Kaiserin, covered a minesweeping operation in the North Sea.

Königsberg, II Scouting Group flagship, was damaged in the engagement, but the four cruisers managed to pull away from the British, drawing them toward the German dreadnoughts.

During the operation, the cruiser Frankfurt suffered damage to her starboard screw, so FK Hans Quaet-Faslem, the deputy commander of torpedo-boats, transferred his flag to Pillau for the rest of the patrol.

Pillau, Cöln, Dresden, and Königsberg were to attack merchant shipping in the Thames estuary while Karlsruhe, Nürnberg, and Graudenz were to bombard targets in Flanders, to draw out the British Grand Fleet.

[30] Admirals Scheer and Franz von Hipper intended to inflict as much damage as possible on the British navy, in order to secure a better bargaining position for Germany, whatever the cost to the fleet.

[31] After the end of the war on 11 November, Pillau was not included on the list of ships to be interned at Scapa Flow, so she remained behind in Wilhelmshaven with a skeleton crew.

Following the German intervention in April 1941 and Greece's defeat, Bari was tasked with escorting convoys from Italy to occupied Greek ports.