Kamikaze drone boats are unmanned or uncrewed surface vessels (USVs) equipped with explosive payload and either remotely controlled or pre-programmed to navigate autonomously. Such vessels are designed to detonate upon impact and, therefore, are also termed suicide drone boats. Historically, these vessels have been used in a limited capacity. But with advancements in technology, these boats are showcasing the potential to emerge as potent weapons, particularly when anti-surface warfare (ASuW) is taken into account.
During World War-I, Germans used remote-controlled suicide boats in the English Channel and the northern European coastline. “Ferlenkboot”, also referred to as FL-boot, was developed by Germans to be used against Royal Navy vessels. The 17m long boat carried 700kg of explosives and was guided by a land station via a 20km long wire spool. The boat carried no sensors, and movement guidance was provided by manned aircraft flying over the employment region. Unreliability and complication in the control system led to the failure of this project. Only a few units were used in combat, with one notable incident in October 1917 when HMS Erebus was damaged by such a boat.
In World War II (WW II), Germans further developed a somewhat similar concept called “Linsen”, an explosive-laden high-speed boat operated by a crew of one. Linsen boats worked in pairs, with one as a control boat and the other as a suicide boat. After moving the boat near the assigned target, the operator bailed out of the boat, and the terminal steering guidance was provided by the control boat via a radio link. The use of suicide boats in varying capacities was reported throughout WW II, but the concept did not deliver any remarkable success.
Integration of high-degree autonomy can enable suicide USVs to operate with more flexibility, minimising their dependency on communication links and thus improving their efficiency in a complex combat environment.
Fast forward to modern times, and we can observe periodic improvements in suicide drone boats primarily due to advancements in guidance mechanisms. Instead of traditional line-of-sight (LOS) targeting based on outdated navigation mediums, modern guidance has enabled over-the-horizon (OTH) targeting capability by using non-line-of-sight (NLOS) navigation systems. Therefore, classical concepts which failed to materialise in the past, primarily due to technological restrictions, can now be employed in a more refined manner.
Since the end of World Wars, some instances have been recorded where unmanned suicide watercraft have been used in combat. For example, during the Iran-Iraq war (1980-1988), the Iranian Navy used explosive-laden unmanned boats to target Iraqi naval and commercial vessels in the Persian Gulf. In 2016, Yemeni Houthi rebels reportedly used a remote-controlled suicide boat to successfully target Royal Saudi Frigate Al-Madinah in the southern Red Sea.
The Russia-Ukraine conflict has seen a relatively wide-scale use of suicide USVs in the Black Sea. On October 29, 2022, Ukraine’s explosive USVs and unmanned aerial vehicles launched a coordinated attack on the Russian Black Sea Fleet stationed in Sevastopol. Though most boats were intercepted, at least two Russian warships – including flag-ship frigate Admiral Makarov and mine sweeper Ivan Golubets – were hit and sustained damage. On June 11, 2023, six suicide USVs attempted to attack the Russian Navy Intelligence Ship “Prizovye” but were successfully countered by the ship’s defensive gunfire. Allegedly, the attack on Crimean Bridge, which damaged Russian logistical lines in Crimea, was also conducted by a suicide drone boat. The Kamikaze USVs have emerged as an efficient asymmetric means to degrade Russia’s ability to exercise uninterrupted navigation in the Black Sea.
In brief, suicide drone boats can conduct a wide spectrum of ASuW operations. There are two distinct employment concepts regarding Kamikaze USVs. First, these boats can be launched from shore to strike enemy surface vessels. Shore-based boats have limited operational range but can be highly efficient at choke points. These boats, particularly when employed in swarms, can saturate the enemy’s defences and establish sea-denial envelop in territorial waters. Enemy assault forces, particularly amphibious crafts, will be vulnerable to such tactics.
Second, these suicide boats can be carried, launched, guided and even recovered from the mother-ship. These boats have low radar and thermal signatures and are meant to operate in conditions too life-threatening for manned vessels. In the offensive employment profile, these nimble suicide boats can be used for targeting enemy ships at sea and for breaching harbour defence. Suicide boats may not be helpful against frontline surface combatants but can threaten supplies and replenishment vessels.
Despite their advantages, Kamikaze drone boats have several technical and operational limitations. First, due to their small size, suicide drone boats typically have limited range and endurance. These boats are predominately sea-denial assets and have little utility in open seas. They cannot reliably operate in high-sea states and adverse weather conditions. Currently, they are helpful against fixed targets, isolated vessels, mines, or ships with poor onboard defensive systems.
Second, suicide USVs are highly vulnerable to kinetic and non-kinetic countermeasures. Once detected, ship-based defences – like deck guns and rapid-fire guns, can neutralise these boats with relative ease. These boats are not equipped with an anti-air defence system. Therefore, aviation assets can effectively thwart them from long ranges.
Third, the Command & Control (C&C) of Kamikaze drone boats are prone to electronic warfare (EW). Electronic counter-measures (ECM), jammers, and decoys can disrupt, confuse, or even disable the sensor suite of these boats. In a communication-denied environment, these boats would have questionable operational utility. Similarly, the C&C of these boats is a challenging undertaking, particularly when OTH targeting is required.
It is worth noting that these boats can be manufactured on a large scale with rudimentary equipment. In the hands of non-state actors, these suicide boats can wreak havoc on commercial shipping lanes. Unlike warships, which are equipped with requisite sensors and defensive systems, civilian vessels are not equipped to counter such a level of threat. The indiscriminate or disproportionate use of suicidal boats by the wrong hands can compromise sea lines of communication (SLOCs), particularly at choke points. Moreover, abandoned Kamikaze drone boats are like floating mines due to loss of control and can endanger unintended vessels.
Despite all the aforementioned limitations, Kamikaze drone boats have the potential to play a significant role in naval warfare. Advances in technology, refinement in military tactics, and evolution in strategic postures will shape the future of Kamikaze drone boats. Integration of high-degree autonomy can enable suicide USVs to operate with more flexibility, minimising their dependency on communication links and thus improving their efficiency in a complex combat environment. Supervised autonomous Kamikaze drone boats can be employed in swarms and in conjunction with other manned-unmanned systems for confusing and overwhelming enemy defences.
In sum, the efficiency of suicide drone boats will vary as per employment tactics and strategic priorities. These boats provide low-cost and low-risk tools for sea-denial operations. Therefore, these boats would be particularly useful for smaller navies postured for sea denial. With improvements in technology, future generations of autonomous Kamikaze boats have the scope to redefine surface warfare.
