June 13, 2017: In early 2017 the Republic of Singapore Navy (RSN) announced that it has ordered two more Type 218SG submarines from a German firm. The first two were ordered in 2013 and will be delivered in 2021 and 2022. The two additional boats are expected to be in service by 2025. The growing threat from China is a major reason for ordering two more of these subs.

The Type 218SG is a variant of the Type 216 that the manufacturer proposed in 2012. A Type 218SG is 70 meters (230 feet) long, displaces 1,800 tons on the surface, has AIP (Air Independent Propulsion) and a lot of electronics built in Singapore and customized for local conditions. These boats are highly automated and thus require a crew of only 28. There are also modifications to improve maneuverability in the shallow waters common in areas adjacent to Singapore. AIP (underwater) endurance is up to 25-30 days and total endurance as much as 80 days. Other modifications make the subs easier to maintain and upgrade. Armament consists of eight forward firing 533mm (21 inch) torpedo tubes and 18 torpedoes or anti-ship missiles. Mines can also be carried. These boats will cost at least $900 million each and this includes training and tech support.

One of the primary local features the RSN shares responsibility for is the Malacca Strait, the busiest shipping choke point on the planet. Most of the world's oil exports pass through the Strait of Malacca as well as much non-tanker cargo. Over 50,000 large ships moved through each year. That’s 120-150 a day. In addition it’s a vital to East Asian economies. The 800 kilometer long strait is between Malaysia and Indonesia and is 65 kilometers wide at its narrowest and depth are generally 27-37 meters (90-120 feet). The shallow and tricky waters in the strait forces the big ships to go slow (under 30 kilometers an hour) to avoid collisions that could easily block the waterway and reduce the flow of traffic.

Singapore has the most effective armed forces in its neighborhood despite being one of the smallest nations in the world. It is a tiny (633 square kilometers) island city state. Defense spending is only about $12 billion a year for a population of 5.2 million. The armed forces consists of 71,000 active duty troops, of which 55 percent are conscripts. But on a per-capita basis, Singapore spends more on the military and has more people in uniform than the United States. The troops are highly trained, not easily replaced and the obvious solution is better weapons and equipment.

Because of this policy the RSN has the most modern ships and the best trained crews in the neighborhood. Currently that fleet consists of four submarines, six frigates, six corvettes, 19 patrol boats, four amphibious ships, four mine warfare ships and one submarine rescue ship. Singapore builds the patrol boats locally and the major warship come from European builders. Singapore has long served as a major naval base, especially for the United States.

Singapore constantly modernizes its warships and replaces them with new models regularly. The current submarine force consists of two recently (2011 and 2012) refurbished Vaastergotland class submarines and four older Challenger class boats, all from Sweden. The Vaastergotland refurb was really a rebuilding of these boats, as their size was increased by a third. The rebuilt boats were renamed the Archer class. The 1,400 ton Archers are 60.5 meters (198.5 feet) long, carry a crew of 28 and are armed with six 533mm and three 400mm (15.75 inch) torpedo tubes. The 400mm torpedo is for other subs, while the larger torpedo is for surface ships. These tubes can also carry mines.

The two Swedish subs were sold to Singapore in 2005, and spent six years being rebuilt and upgraded. For example, the boats now have air conditioning and other mods useful for subs spending all their time in tropical waters. In addition to new electronic systems, the boats have AIP, which accounts for most of the added size. Surface speed is 15 kilometers an hour, while submerged speed is 28 kilometers an hour. These two boats replaced two of the older Challenger class subs. These were purchased in 1995 from Sweden where they were Sjöbjörnen Class subs that entered service in the late 1960s. For Singapore the Challenger class were refurbished for tropical conditions as well as weapons system and sensor upgrades. These submarines performed very well in exercises against American and Australian warships, proving that these old boats, when handled well in littoral conditions, are quiet and maneuverable subs that are able to give a pretty good account of themselves.