In 1936, after he completed the latter studies, Lieutenant Fisanovich began serving in the Baltic Fleet, first as navigator, then as commander of a submarine. In the summer of 1938 he was transferred to the Northern Fleet.
On July 22, 1941 he was named commander of an M-172 submarine (nicknamed "maliutka" or "tyke"). On August 21 Fisanovich's ship was the first of its class to break into an enemy port and destroy an enemy transport ship being unloaded at a dock. A day later the maliutka destroyed another enemy ship. Thus, Fisanovich became the first submarine commander of the Northern Fleet to sink two transport ships in one operation. For this and other services Fisanovich was awarded the Order of the Red Banner and, on April 3, 1942, he was honored as a Hero of the Soviet Union. His submarine was honored by having the Order of the Red Banner attached to its flag. Such an honor was bestowed only four times in the history of the Soviet navy.
In the course of two years Fisanovich's ship engaged in 17 battles. It sank two large battleships, 10 ships, and one tanker. It took part in landing intelligence agents in the enemy rear and in later evacuating them. Due to his achievements Fisanovich's name was well known during the war. He was a member of the Jewish Anti-fascist Committee. Fisanovich had become the symbol of the participation of Jews in modern warfare.
Itsik Fefer wrote about him as follows: "His grandfather, a melamed from Konstantingrad, might well have said: 'underwater my Isrolik is like the prophet in the belly of the fish.'" (Itsik Fefer, "Yisrael Fisanovich, der held fun Sovetn-farband," Eynikayt, June 28, 1942). In his essay Fefer cited Fisanovich's appeal to American Jews that was delivered as part of the Jewish Anti-fascist Committee's campaign to mobilize support for the fight of the Red Army against the Nazis:
"It would be very good if our American brothers would build a submarine for the Red Army, in addition to tanks and bombers. I already have some experience and, as a member of the Jewish Anti-fascist Committee, I would undertake to deliver this ship from America [to the USSR]… What do you think, is this a good idea? That would be useful for our struggle and I would thus be able to justify the honor I have as a member of the Jewish Anti-fascist Committee…."
Firsanovich did receive this opportunity but that was his last military operation. In July 1944 Captain 2nd class Fisanovich and his crew were taking one of four British B-1 submarines from Scotland to a Soviet base in the polar region. However, the ship did not reach its goal. Only after the war did it become known that on July 27, 1944 the ship was sunk by mistake by the British coast guard.
In 1944 Der Emes publishing house in Moscow issued a brochure by Veniamin Kaverin in Yiddish called The Hero of the Soviet Union, Yisroel Fisanovich.
- Jews in the Red Army, 1941–1945