Due to its proximity to Singapore and Peninsular Malaysia, the Riau Islands area became the focus point during the Indonesia–Malaysia confrontation. During this period, the territorial waters of the Riau Islands began to be visited by many Indonesian military forces who were members of the Indonesian Operations Command Corps or better known as the Indonesian Marine Corps. The city of Batam became one of the staging point of Indonesian troops during the confrontation, with the construction of military bases around the city. Anti-Malaysian guerrillas were gathered at Tanjung Balai Karimun to be trained and then sent to Sambu Island for briefing before operation. These guerrillas aimed to sabotage and spread information to help Indonesia fight the British in Malaysia, causing the economy around the Riau Islands, especially Tanjung Balai Karimun, does not function normally due to these military activities. At that time, KOPASKA special forces of the Indonesian Navy infiltrated Singapore from military bases in the Riau Islands, around Batam, Tanjung Balai Asahan and the surrounding area. They usually use small boats with outboard motors and disguise themselves as local residents who usually have relatives on the Malay Peninsula and Singapore. The coastline of Batam and the surrounding islands were heavily fortified to deter possible British and Malaysian invasion.