As I read the story (seems to be more unsaid than said), the Brits were trying to recover stolen weapons and punish the perpetrators, among whom they thought was the hapless Elihu Sacharoff.
And this particular sentence is startling, since Sacharoff was a body-guard for Zionist President Chaim Weizmann, who became Israel's first president in 1949.
At this point in 1943, Chaim Weizmann was working hard to establish a 5,000 man Jewish Brigade, which was finally approved by the Brits in 1944 and served in northern Italy.
Training and experience received by the Jewish Brigade benefitted Israel in its War of Independence.
So it's not surprising that Weizmann would be doing everything he could to collect arms and ammunition.
But, I'm just guessing, Sacharoff probably did not serve the full term of his sentence.
Weizmann (fr row, 2nd from left) with Arab & Zionist leaders in 1933, King David Hotel, Jerusalem: