When did Indonesia nationalism begin to develop?

Indonesian nationalism began to develop in the early 20th century, with significant momentum gained during the Dutch colonial period. The establishment of organizations such as Budi Utomo in 1908 and Sarekat Islam in 1912 marked the initial efforts to promote national consciousness among Indonesians. The movement intensified in the 1920s and 1930s, culminating in the declaration of Indonesia's independence on August 17, 1945, following years of struggle against colonial rule.