The Chazon Ish was asked by a Talmid if he may join the army. The Talmid said that he would remain frum but being in the army environment would cause him to feel less passionate and colder [קאלטקייט] with regard to Avodas Hashem.
The Chazon Ish said that coldness towards Avodas Hashem is יהרג ואל יעבור.
