Aleksandr Isayevich Solzhenitsyn (; 11 December 1918 - 3 August 2008) was a Russian novelist, historian, and short story writer. He was an outspoken critic of the Soviet Union and communism and helped to raise global awareness of its Gulag forced labor camp system. He was allowed to publish only one work in the Soviet Union, One Day in the Life of Ivan Denisovich (1962), in the periodical Novy Mir.

During the war, Solzhenitsyn served as the commander of a sound-ranging battery in the Red Army, was involved in major action at the front, and was twice decorated. He was awarded the Order of the Red Star on 8 July 1944 for sound-ranging two German artillery batteries and adjusting counterbattery fire onto them, resulting in their destruction.  A series of writings published late in his life, including the early uncompleted novel Love the Revolution!, chronicles his wartime experience and his growing doubts about the moral foundations of the Soviet regime.  While serving as an artillery officer in East Prussia, Solzhenitsyn witnessed war crimes against local German civilians by Soviet military personnel. The noncombatants and the elderly were robbed of their meager possessions and women and girls were gang-raped to death. A few years later, in the forced labor camp, he memorized a poem titled "Prussian Nights" about these incidents. In this poem, which describes the gang-rape of a Polish woman whom the Red Army soldiers mistakenly thought to be a German, the first-person narrator comments on the events with sarcasm and refers to the responsibility of official Soviet writers like Ilya Ehrenburg.  In The Gulag Archipelago, Solzhenitsyn wrote, "There is nothing that so assists the awakening of omniscience within us as insistent thoughts about one's own transgressions, errors, mistakes. After the difficult cycles of such ponderings over many years, whenever I mentioned the heartlessness of our highest-ranking bureaucrats, the cruelty of our executioners, I remember myself in my Captain's shoulder boards and the forward march of my battery through East Prussia, enshrouded in fire, and I say: 'So were we any better?'"

Using a quote from the above article, answer the following question: Where did he serve during the war?
East Prussia,