Often riding his horse to outlying parts of the district, Wallace was very popular and likeable, described as "of good moral character, and fine manly qualities", according to the Illawarra Remembers project.

Wallace was part of the first raid on Amman on March 22, 1918, which was intended to inflict casualties on Turkish forces and sever railway communications with Damascus. Rain made going extremely difficult, but by the evening of March 25, the village of Es Salt had been taken. On the morning of March 27, the attack began on Amman and fierce fighting continued for two days.

Sadly, Wallace was among the 118 Allies who died during the offensive, while another 55 were reported missing. He was originally listed as missing and his family lived in hope for almost a year, until they received the devastating news of his death.

According to the Red Cross wounded and missing report: "Informant states that on the 28/3/18, the Regiment was in action against the Turks at Amman east of the River Jordan in Palestine. During the advance, Sharpe was hit by machine gun fire, together with two or three others. Informant was about 50 yards away, and saw all the men hit, lying on the ground. He recognised Sharpe who was still alive.

"I knew Sergeant Sharpe by sight. He was a tall man standing about 6ft. of big build, dark, clean shaved. He went out with Liet. Ridgway's party, when they made an unsuccessful attack on Amman. We were in support; Ringrose was the only man of the party who returned. He reported that everyone of them had been hit. This was on the 28th March, 1918. Another attack was made on Amman 6 months after this and the place was taken. Some of us went out to see the place where Liet. Ridgeway's party had been attacked. The dead bodies were lying there just as they had fallen, and we buried them. Sharpe was identified by some of the men. Sharpe was one of the most popular men in the Regiment - He was a great leader of men."

Four years later, his mother Mary wrote to the Officer in Charge of base records, pleading for information about where her son was buried. "He was killed on the hills of Amman and I have never heard where his body was laid. I have been looking through books lately received but not knowing what cemetery I am still in the dark. If you have any clue, would you kindly let me know, if not troubling you too much, thanking you in advance."

A plaque in Wallace's memory is in the Jerusalem War Cemetery in Israel, as well as a memorial inside the Gerringong Uniting Church. His name is located at panel five on the Roll of Honour at the Australian War Memorial in Canberra.