The Scheinermans' eventual ostracism... followed the 1933 Arlozorov murder when Dvora and Shmuel refused to endorse the Labor movement's anti-Revisionist calumny and participate in Bolshevi(k)-style public revilement rallies, then the order of the day. Retribution was quick to come. They were expelled from the local health-fund clinic and village synagogue. The cooperative's truck wouldn't make deliveries to their farm nor collect produce. In 1942 at the age of 14, he joined the Gadna, a paramilitary youth battalion, and later the Haganah, the underground paramilitary force and the Jewish military precursor to the Israel Defense Forces. At the creation of Israel (and Haganah's transformation into the Israel Defense Forces), Sharon was a platoon commander in the Alexandroni Brigade. Sharon was severely wounded in the groin by the Jordanian Arab Legion in the Second Battle of Latrun, an unsuccessful attempt to relieve the besieged Jewish community of Jerusalem. His injuries eventually healed.

In September 1949, he was promoted to company commander (of the Golani Brigade's reconnaissance unit) and in 1950 to intelligence officer for Central Command. He then took leave to begin studies of history and Middle Eastern culture at the Hebrew University of Jerusalem. A year and a half later, he was asked to return to active service in the rank of major and as the leader of the new Unit 101, Israel's first special forces unit.

Unit 101 undertook a series of retaliatory raids against Palestinians and neighboring Arab states that helped bolster Israeli morale and fortify its deterrent image. However, the unit was also known for targeting civilians as well as Arab soldiers, notably in the widely condemned Qibya operation in the fall of 1953, in which 69 Palestinian civilians, half of which were women and children, were killed by Sharon's troops in a reprisal attack on their West Bank village. In the documentary "Israel and the Arabs: 50 Year War" Ariel Sharon recalls what happened after the raid, which was heavily condemned by many countries in the West, including the U.S.:

I was summoned to see Ben-Gurion. It was the first time I met him, and right from the start Ben-Gurion said to me: "Let me first tell you one thing: it doesn't matter what the world says about Israel, it doesn't matter what they say about us anywhere else. The only thing that matters is that we can exist here on the land of our forefathers. And unless we show the Arabs that there is a high price to pay for murdering Jews, we won't survive." Shortly afterwards, just a few months after its founding, Unit 101 was merged into the 202nd Paratroopers Brigade (Sharon eventually became the latter's commander), which continued to attack military and civilian targets, culminating with the attack on Qalqilyah police station in autumn 1956.

As reflected in the above-mentioned episode, Sharon - while formally no more than a middle-ranking officer at the rank of Rav Seren (Major) - had direct access to the Prime Minister as well as to then Army Chief-of-Staff Moshe Dayan, bypassing the normal chain of command.

Ben Gurion and Dayan, as well as Sharon himslef, were well aware that the actions of his commando unit had a significant role in shaping Israel's relations with its neightbors, and that such raids could become the subject of headlines in the international press and debates in the UN.

Perforce, Sharon was already at this stage of his career involved in strategic considerations which are normally the province of senior officers and of the political echelon. Moreover, historians often point to this period as shaping Sharon's habit of acting on his own judgegment and ignoring or circumventing the instructions of his direct superiors.

Sharon has been widowed twice. Shortly after becoming a military instructor, he married his first wife, Margalit, with whom he had a son, Gur. Margalit died in a car accident in 1962. Their son, Gur, died in October 1967 after a friend shot him while they were playing with the elder Sharon's rifle. After Margalith's death, Sharon married her younger sister, Lily. They had two sons, Omri and Gil'ad. Lily Sharon died in 2000.