Wikipedia
The Perushim were disciples of the Vilna Gaon, Rabbi Elijah ben Solomon Zalman, who left Lithuania at the beginning of the 19th century to settle in the Land of Israel, which was then part of Ottoman Syria under Ottoman rule. They were from the section of the community known as mitnagdim (opponents of the Chassidic movement) in Lithuania.
The name Perushim comes from the parash, meaning "to separate". The group sought to separate themselves from what they saw as the impurities of the society around them in Europe, and the name literally means 'separated (individuals)'. Coincidentally this was the same name by which the Pharisees of antiquity were known. However the latter-day Perushim did not make any claim to be successors of the Pharisees. In the generations prior to their departure for Israel, the term "Perushim" (spelled in Hebrew פירושים) referred to commentaries in the sifrei kodesh (holy books). It was later applied to the Vilna group, alluding to their practice of studying Biblical commentaries, not just the Talmud and later commentaries.
Influenced by the Vilna Gaon, who had wanted to go to Eretz Yisrael but was unable to do so, a large group of his Perushim disciples and their families, numbering over 500, with a few dozen younger earlier scouts, were inspired to follow his vision. Enduring great hardships and danger, they traveled to and settled in the Holy Land, where they had a profound effect on the future history of the Yishuv haYashan- the Old Yishuv. Most of the Perushim settled in Safed, Tiberias, Jaffa and in Jerusalem, setting up what were known as the Kollel Perushim, and forming the basis of the Ashkenazi communities there.
Thus the Perushim were one of the only groups of religious Jews that did not face the Holocaust in Lithuania and Estonia, and the only major established group of poor Lithuanian and Estonian Jews that did not experience the Holocaust. The conflict between Chassidic and non-Chassidic Jews was ended by World War II, as the old religious Jewish presence in those countries was destroyed. Most of these people, although they influenced the State of Israel especially through the creation of crafts, newspapers and daycare for Jews, left in the 1930s. Like most deeply religious poor Jews, they were very hesitant to serve in any army or militia. The majority of their descendants established themselves in middle-class neighborhoods of the America and Australia. The phenomenon of Orthodox refusal to serve in the Israeli military remains a divisive issue in modern Israel.
In contrast, and although his was the minority position, the first Chief Rabbi of Israel and the most respected Mitnagged scholar of his generation Abraham Isaac Kook, promulgated opinions requiring all Jews to serve in Israel's militias in any way they could. Later, when the Haggannah developed into the IDF and following the formation of the State of Israel, Chief Rabbi Kook had public symbolic meetings with Israeli generals, and with David Ben-Gurion. Thus the first Chief Rabbi marshaled religious support for Jewish nationalism.