Sannyasa (संन्यास saṃnyāsa) is the life stage of renunciation within the Hindu philosophy of four age-based life stages known as ashramas, with the first three being Brahmacharya (bachelor student), Grihastha (householder) and Vanaprastha (forest dweller, retired). Sannyasa is traditionally conceptualized for men or women in late years of their life, but young brahmacharis have had the choice to skip the householder and retirement stages, renounce worldly and materialistic pursuits and dedicate their lives to spiritual pursuits. Sannyasa is a form of asceticism, is marked by renunciation of material desires and prejudices, represented by a state of disinterest and detachment from material life, and has the purpose of spending one's life in peaceful, love-inspired, simple spiritual life. An individual in Sanyasa is known as a Sannyasi (male) or Sannyasini (female) in Hinduism,[note 1] which in many ways parallel to the Sadhu and Sadhvi traditions of Jain monasticism, the bhikkhus and bhikkhunis of Buddhism and the monk and nun traditions of Christianity. Sannyasa has historically been a stage of renunciation, ahimsa (non-violence) peaceful and simple life and spiritual pursuit in Indian traditions. However, this has not always been the case. After the invasions and establishment of Muslim rule in India, from the 12th century through the British Raj, parts of the Shaiva and Vaishnava ascetics metamorphosed into a military order, to rebel against persecution, where they developed martial arts, created military strategies, and engaged in guerrilla warfare. These warrior sanyasis (ascetics) played an important role in helping European colonial powers establish themselves in the Indian subcontinent.