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Sri Lanka learns to counter Sea Tigers’ swarm tactics

by Tim Fish

As Sri Lanka celebrated its Independence Day on February 4, the Sri Lanka Army was closing in on the last pockets of resistance occupied by fighters from the separatist group Liberation Tigers of Tamil Eelam (LTTE) in their jungle hideaways. After almost three decades of violent conflict, the government appeared confident that victory in the struggle for control of the island was finally within sight.

The LTTE’s last major stronghold at Mullaitivu on the northeast coast of Sri Lanka fell on January 25, forcing 2,000 rebels to flee into the hinterland. The loss of the town followed the seizure by government forces of the LTTE’s self-proclaimed capital, Kilinochchi: the culmination of the steady collapse of the rebels’ power base. The LTTE had been gradually losing its influence over Sri Lankan territory following the collapse of an UN-brokered ceasefire agreement in 2006.

By mid-February 2009, four army divisions consisting of 50,000 troops were moving in on the last rebel positions, leaving the remnants of the LTTE with little hope of survival. Bringing the conflict to a conclusion after 30 years of war would not have been possible without the Sri Lanka Navy (SLN). Throughout this period, the SLN had to evolve from its post-independence ceremonial role into a war fighting force capable of confronting a well-armed opponent possessing expert asymmetric-warfare skills in the maritime domain. The LTTE’s naval wing — known as the Sea Tigers — had just 30 km of coastline left under its control as JNI went to press, and this was rapidly being closed off by government forces.

Constantly patrolled

The area is constantly patrolled by what the SLN terms “defence barriers” of vessels four layers deep, consisting of fast attack craft (FAC), offshore patrol vessels (OPVs), gun boats, and the SLN’s Rapid Action Boat Squadron (RABS) and Special Boat Squadron (SBS), eliminating the LTTE’s seaward escape route and preventing supplies from reaching the rebels. This level of proficiency is a significant advance from the SLN’s capabilities of the 1950s–70s. The service was created in 1950 to assist fishermen, provide search-and-rescue services, prevent illegal immigration and smuggling, and aid the civil power in a national emergency. However, when the LTTE’s Sea Tigers wing was created in 1984, the fledgling insurgent force used small boats to ferry guerilla fighters and equipment across the 16 km-wide strait that separates the Indian state of Tamil Nadu from the Jaffna Peninsula at Sri Lanka’s northern tip. The SLN made attempts to put a halt to these operations and achieved some degree of success using patrol boats.

However, the LTTE began using faster craft with more powerful engines, allowing the Sea Tiger cadres to outrun the slower SLN patrols. The Sea Tigers were able to transport large shipments of weapons across the Palk Strait from India to Sri Lanka, forcing the navy to look overseas for a solution. Vice-Admiral Wasantha Karannagoda, Commander of the SLN, says: “We found that the SLN did not have a suitable boat to meet this threat. We looked around the world and saw the Israeli navy was facing a similar threat and were using Dvora fast attack craft as a response.” Sri Lanka bought its first pair of 47 ton Dvora-class FAC from Israel in early 1984 and another four were purchased in 1986. An upgraded version — the 54 ton Super Dvora Mk I — was ordered from Israeli Aircraft Industries (IAI) in October 1986 and delivered from 1987–88, with a further four Super Dvora Mk II-class FAC delivered in 1995–96. “We bought [the Dvoras] and first put them into action in the late 1980s, and the Sea Tigers found it very difficult to meet these Israeli-built craft,” says Vice-Adm Karannagoda. “But then to counter this, the LTTE developed very high horsepower suicide boats and used swarming tactics to overwhelm the Dvoras, which in our view could not tackle them effectively.” During the 1990s, the LTTE scored some significant hits against the Israeli-built craft, sinking a Dvora-class FAC on 29 August 1995 and a second vessel on 30 March 1996. The Sea Tigers also sank two Super Dvora Mk I-class vessels on 29 August 1993 and again on the same day in 1995.

Two Super Dvora Mk II boats were sunk in 2000. The LTTE also enjoyed success against the SLN’s other classes of FAC, sinking a 68 ton United States-built Trinity Marine class craft, two Shanghai II-class craft (acquired from China in 1991) and three domestically built Colombo-class craft. However, Sri Lankan security forces were able to recapture the Jaffna Peninsula from the LTTE in 2002 during Operation ‘Riviresa’, in which the SLN played a major role by providing transport for troops and supplies, and by patrolling the Palk Strait. At the time, the area was cut off from the rest of the government-held territory to the south, which meant that providing naval transport services to the region became a long-term tasking.

Asymmetric conflict a ceasefire was negotiated in 2002, lasting for four years, but the Sea Tigers had increased their strength by the time hostilities resumed in 2006. In the area known as Adam’s Bridge, from Pamban to Mannar, the waters are extremely shallow. Shifting sands can reduce depth to less than 1 m and rapid changes can cause problems for large-displacement ships with a deep draft. Some of the SLN’s larger patrol craft were unable to access this area of sea safely to intercept the Sea Tigers. Dvora FAC typically needs 1.8–2 m water depth. “During this period, the LTTE improved the suicide concept, developing bigger boats with faster speed, and the Dvoras could not match this,” says Vice-Adm Karannagoda. “When the ceasefire ended, we found the LTTE Sea Tigers were very strong and were coming at us with faster and stronger boats.

The Dvoras were finding it very difficult in battles at sea with normal fighting craft against about 15 Sea Tiger craft and another eight to 10 suicide craft, which would sometimes mingle with fishermen.” Identifying the suicide boats in a swarm of Sea Tiger craft was difficult as the former appeared identical to the insurgents’ regular attack boats. SLN crews would have to watch for subtle differences in the behaviour of the craft, monitoring their movements and noting if they were heavier in the water in order to identify them; this was not a skill that could be taught in the classroom. Suicide boats had to be identified and destroyed swiftly, as given time they would attack in a pack of five or six in an attempt to overwhelm the SLN crews. With a low profile and moving at 35–40 kt, the suicide craft were very difficult to engage with gunfire and some were armoured at the front, meaning small-calibre rounds would ricochet off. Battles involved numerous small craft and intense close-quarters action between boat crews within a 2 km range. The Sea Tigers’ larger craft had four 250 hp petrol outboard motors, while the small boats were equipped with two: if one motor was damaged the other could be used to effect an escape. Vice-Adm Karannagoda says: “We had to counter this situation so our engineers did some extensive research-and-development [R&D] work and developed three categories of new boats. With this we developed our Small Boats Concept, which was a major turning point in the progress of the war.” The Small Boats Concept effectively copied the Sea Tigers’ asymmetric tactics, but on a much larger scale.

Ceremonial Navy to Fighting Navy

The SLN started to use large numbers of small high-speed heavily armed inshore patrol craft (IPC) to outnumber the LTTE suicide boats and overwhelm them during battle. Hundreds of indigenously produced fibreglass IPC have been built in three variants for operations in different sea states. The smallest is the 23 ft-long Arrow; a second class is 14 m long, with both types able to operate in conditions up to Sea State 3. A third variant — a 17 m command-cum fighting boat — can cope with conditions up to Sea State 4. “We manufactured these boats day and night, because we needed them quickly, and this is how we were able to tame the Tigers at sea,” says Vice-Adm Karannagoda. Service transformation “From a ceremonial navy we transformed ourselves into a fighting navy. Now, whilst performing the earlier constabulary duties, we are also fighting the LTTE and ensuring the safety of sea lines of communication, security of harbours, escorting merchant vessels to the Jaffna Peninsula, transporting troops from Trincomalee, and surveillance of the EEZ [exclusive economic zone] and territorial waters to prevent the LTTE from bringing in arms and ammunition.” The 14 m and 17 m boats are fitted with four 250 hp engines, giving a top speed of 37 kt. Armaments include a double-barrelled 23 mm gun, CIS 40 mm Automatic Grenade Launcher (AGL) acquired from Singapore Technologies Kinetics and two 12.7 mm (.50 calibre) machine guns.

The smaller Arrow boats have two 250 hp engines for a top speed of 35 kt and are equipped with a single-barrel 23 mm gun or a .50 calibre gun and an AGL. The Dvora FAC has been upgraded with 30 mm guns and the SLN has used its own engineers to integrate the Bushmaster M242 25 mm gun on to the deck during sea acceptance and harbour acceptance trials. Bushmaster is built by USbased Alliant Techsystems, which transferred the guns to Sri Lanka under US State Department guidelines. “In 2007 we put [the Dvoras] into action after integrating [Bushmaster] ourselves in Sri Lanka. It cost us just the price of the guns; we did not have to pay the price of integration,” says Vice-Adm Karannagoda. The advantage that the Dvora FAC has over the smaller IPC is that it is able to remain at sea for longer periods to conduct surveillance missions, as well as engage in fighting to control the sea lines of communication. Because the LTTE boats were hidden and could only operate in short-duration missions, they were able to select the time and place of their attacks, and therefore the SLN had to maintain round-the-clock surveillance so as to be ready for them. Following the purchase of the FAC from Israel, the SLN began to build its own versions of the craft in Colombo Dockyard.


The Dvoras “are boats that can take to the sea and are comfortable at sea, whereas the small boats we have built are mission-orientated”, he says. “When we see a confrontation looming, the IPCs are launched and take the Sea Tigers on: that is how we neutralise the enemy totally at sea.” The new IPCs are built using GRP materials and a boat mould to provide a frame for the fibreglass hull. It takes just 45 days to complete and fully equip a single craft. At sea, the IPCs operate in groups of four craft. Several groups — totalling 25–30 craft — combine to form IPC squadrons, which are based at strategically important locations around Sri Lanka.

The IPC squadrons are organised for rapid-reaction interception operations, because the Sea Tiger cadres have been able to remain hidden until they decide to confront the SLN. The Sea Tigers’ ability — at least until recently — to dictate when a naval action will occur means the SLN has to maintain 24-hour surveillance and remain prepared to intercept any movement. To maximise the amount of firepower each squadron can bring to a battle, an IPC squadron would speed towards the enemy using strategies that echo infantry tactics: an arrowhead formation is used to expand each boat’s arc of fire in an attack manoeuvre, or boats are arranged in three adjacent columns in single file so as to mask their numbers and increase the SLN’s element of surprise.

Sea Tiger assets

The enemy consisted of hundreds of Sea Tiger fibreglass boats in four main types: the 45 kt Thrikka, with four crew and a machine gun, has been used to deploy frogmen; the 10 kt Sudai, also armed with a single machine gun, has been used to attack naval craft; the 45 kt Muraj, with a crew of 10 and three machine guns, has also been used for attacks against naval craft, as well as for inserting land-attack teams; and the two-man Idayan was a 45 kt suicide craft fi tted with explosives and designed to detonate on impact. Without harbours or secure launching areas, the LTTE used trailers to launch and recover their craft. Following a mission, the boats would be taken into the trailers and either a tractor or bulldozer would pull them 2–3 km inland from the beach to avoid detection by the Sri Lanka Air Force (SLAF). Because the separatists would remain hidden for long periods, bringing them to action required a high degree of flexibility and training from the IPC squadrons because they would have to wait for and respond to the sudden deployment of the Sea Tigers.

The SLN’s ability to concentrate a force at short notice that was able to confront the Sea Tigers was an important factor in gaining the upper hand in sea battles. “In a very short period of time, we can shift one whole squadron to another place, so at some locations we have combined [squadron] numbers and have had up to 60 boats available in some battle situations,” says Vice-Adm Karannagoda. Using small, fast and well-armed IPCs to best effect requires highly trained sailors. Two new units were created for this purpose: the SBS and the RABS. The SBS was established on 22 October 2005 with 36 personnel and now numbers 600. It is the SLN’s elite force, possessing high levels of physical fitness and advanced training in both land and sea warfare tactics. The SBS operates in four- to eight-man teams using the Arrow boats for rapid insertion or black rubber inflatable boats for covert approach from the sea. The teams have expertise in long-range communications and engage primarily in surveillance operations, providing a much-needed source of information on LTTE activities. The teams also undertake reconnaissance and land-strike missions.

(These Extracts from an article in Jane’s Navy International of March 2009 were published in the "Nation" of March 15th 2009)

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