The Dutch real interest in the island came in the 19th century. The military expeditions to Bali were ordered by governor general Rochussen himself because the princes of Buleleng and Karang Asem refused to acknowledge Dutch supremacy.
In 1846 the first military expedition was sent to Bali. After the landing the Dutch soldiers discovered that the Balinese were formidable enemies and had better firearms (bought in Singapore) than the KNIL. A treaty was signed with the Balinese kings. On paper it was a Dutch success, but they soon realized that the Balinese forces were not defeated but had imply withdrawn. The Balinese paid no attention at all to the agreement and even refused to sell food to the soldiers in the Dutch fort in Buleleng. The result was a second invasion in 1848 that ended in a complete defeat before the field fortification of Jagaraga. The third war in 1849 had more success and the kingdoms of Northern Bali recognized the Dutch supremacy.
The defenses at Jagaraga were demolished.
Between 1849 and 1892 the Dutch did not interfere in the internal affairs of the kingdoms in South and East Bali. At the end of the century the unoccupied part of Bali became a battlefield between the independent Balinese kingdoms. Batavia watched and wait.
In 1849 the Balinese lords, which ruled Lombok, accepted Dutch sovereignty. The relations with Batavia changed when in 1891 the Balinese raja of Lombok send troops to fight on Bali.
The first Dutch invasion in 1894 was defeated with the heavy losses. Several months later the reinforced KNIL came back and occupied the capital Mataram. The Balinese stronghold Cakranegara was taken after the Balinese royal family died in a heroic last suicidal attack (puputan).
Dutch complaints about slavery, opium, the burning of widows and the plundering of a shipwreck led to a growing tension with the independent states in south and east Bali. In 1906 the Dutch attacked Badung where the royal households of Den Pasar and Pamecutan died in a suicide attack against the Dutch. The Dutch conquest of the island ended in 1908 with the puputan of the royal household of Klungkung
On the eve of the Second World War the Dutch didn't take much care of the defense of Bali.
and Lombok The only defense on Bali was a coastal battery near Den Passar airfield.
On February 18, 1942 at Japanese invasion force landed on the south coast of Bali and occupied the island without opposition of the KNIL. The loss of Bali was a severe set back for the defense of Java. The airfield on the island was not destroyed and the Japanese fighterplanes soon blocked the transport of new warplanes from Australia to Java.
The Japanese expected an allied invasion from the direction of Australia. On Bali and Lombok defenses were built to stop a landing.