Why was Juliek concerned about his violin after the forced march from Buna?

When the Polish musician Juliek, who worked in the electrical warehouse at Buna, speaks to Elie among the crush of men who have come to the barracks at Gleiwitz, he is fearful that his violin will get broken in the chaos. He has brought it with him on the deadly forced march from Buna. Elie is shocked that Juliek is worried about a violin:

I thought he had gone out of his mind. What use was a violin here?

Later, after fighting for air and his life in the claustrophobic pile of dead and dying men, Elie hears a violin. It was Juliek playing a fragment from a Beethoven concerto. Elie realizes why Juliek has brought his violin. It is his last connection with life and civilization. Instead of being reduced to a wild savage fighting for a morsel of bread, Juliek plays the violin, proving his worth as a man and an artist:

He was playing his life. The whole of his life was gliding on the strings—his lost hopes, his charred past, his extinguished future. He played as he would never play again.

Juliek refuses to go out as a victim. He is, instead, a rebel. Playing the Beethoven concerto was his last attempt at rebellion against his bitter fate. The Germans had prohibited the Jews from playing compositions from German composers. Juliek thumbs his nose at this restriction and in the last moments of his life. When Elie wakes up the next morning, Juliek is dead and his violin crushed.