From Alexander using Jhelum River in 326 BC to dams and flooding in modern world: How rivers have been weaponised to win wars and gain tactical advantage

It was 326 BC. Alexander stood on the banks of the Jhelum River, known as Hydaspes at that time, and plotted a masterstroke against King Porus of Punjab. Porus was confident that the swollen river would shield him from attack as he waited on the opposite shore with war elephants.

However, under the cover of darkness and storm, Alexander’s troops moved upstream and forded the raging waters. Alexender kept sending troops slowly every night while projecting as if he was waiting for the river to cool down. They caught Porus’s army in a deadly fight at dawn one day. The young Macedonian conqueror snatched victory from Porus’s hands by turning the river into an unexpected ally and wrote his name into history. This little lesson of history shows that rivers have been weaponised to win wars and gain tactical advantages — and today’s times are no different.

The Indus Waters Treaty – Water as leverage in South Asia

Fast forward over two millennia, and the strategic use of rivers is still very much alive. In April 2025, India announced that it would suspend the Indus Waters Treaty (IWT) with Pakistan. It is a 63-year-old water-sharing pact which, interestingly, survived multiple wars between the arch-enemies, India and Pakistan.

The drastic move came after Pakistan-sponsored terrorist organisation Lashkar-e-Taiba’s offshoot, The Resistance Force (TRF), killed 27 innocent tourists in Pahalgam, Jammu and Kashmir. The terrorists associated with TRF questioned the tourists if they were Hindus or Muslims. They forced them to read the Kalma and checked if they were circumcised. If the victims failed in any test, they were shot dead by the terrorists, who left the women and killed only men. When one of the victim’s wives dared the terrorists to shoot her as well, one of the terrorists told her to “Tell Modi”.

The devastating Pahalgam terrorist attack sent shockwaves across India. The Government of India, while accepting there was a security lapse, initiated several steps to counter-attack Pakistan on every front. India suspended visas issued to Pakistani nationals and started deporting Pakistanis living in India, even if they had come on medical visas. Only persecuted Pakistani Hindus were exempted. In one of the strongest moves, India suspended the IWT with Pakistan and hinted it might turn off the tap of the Indus basin rivers until Islamabad reins in cross-border terrorism.

Pakistan reacted with outrage and said that if India suspended the water supply, it would be an act of war. The hostile neighbour vowed to respond “with full force” if India choked the rivers. Pakistan is a downstream nation. It acutely depends on the Indus and its tributaries for agriculture, power, and drinking water.

India, which is an upstream nation, possesses a natural hydrological high ground. The Indus’s headwaters and five major tributaries flow from the Himalayan mountains in India into Pakistan. In theory, India has the power to control how and when water flows across the border.

Pakistan is well aware of the situation and, interestingly, it was Pakistan which benefitted from the IWT that was signed in 1960. Under the treaty, the eastern rivers were allocated to India and the western rivers, including the Indus, Jhelum and Chenab, to Pakistan. India promised, under the treaty, that it would never restrict the water. However, as India has now suspended its participation, with negligible chances of retracting from the decision, New Delhi has indicated that this promise has been withdrawn. In simplest terms, it is a potent form of pressure short of armed conflict.

Notably, this is not the first time India has warned of suspending the treaty. In 2016, Pakistani terrorists affiliated with the Jaish-e-Mohammed terrorist outfit attacked an army base in Jammu and Kashmir’s Uri and killed 19 soldiers. Around 30 were injured. At that time, Prime Minister Narendra Modi, who was in his first term as the PM, warned that “blood and water cannot flow together,” implying the Indus pact could be scrapped if violence continued.

In 2019, after India abrogated Article 370 in Jammu and Kashmir, New Delhi came close to unilaterally walking away from the treaty. However, India held back at that time. This year, India has put the IWT actively on hold. Notably, India is yet to divert or stop Pakistan’s share of water. However, the message is clear: India has the power to choose the right time to stop the water, and Pakistan will have no power to do anything to stop New Delhi from doing it.

Indus waters have become a bargaining chip for India, which already has higher stakes in the Global South. India has friendly relations with most of the South Asian countries. Pakistan, on the other hand, is struggling financially. The hostile neighbour keeps begging Middle Eastern countries for funds to run the country and is currently under a lot of debt.

From electricity to basic food items like flour and tomatoes, everything is getting more expensive every day in the country. Still, Pakistan thinks it can afford a full-fledged war with India — that too when India has the power to control the water flow to over a majority of its agricultural fields. India’s upper hand in controlling the water flow is a clear example that rivers, like armies, can be marshalled for geopolitical advantage.

Ukraine – Flooding the frontlines of war

Water has proven to be a decisive force in 21st-century conflicts. When Russia launched its military attack on Ukraine in 2022, Kyiv weaponised rivers and dams to stall the Russians. In the early weeks of the war, Ukrainian engineers breached a Soviet-era dam on the Irpin River northwest of Kyiv. They deliberately flooded around 13,000 hectares of wetlands. Several villages, like Demydiv, were submerged, creating a swampy barrier that stopped advancing Russian tanks. Though dozens of homes and vast farmland were lost, the strategy saved Kyiv from the initial attack. Irpin was hailed as the “Hero River” that helped defend the city.

Interestingly, Russia later adopted similar tactics. In September 2022, retreating Russian forces launched a missile strike on a dam in Kryvyi Rih. It caused the Inhulets River to overflow and parts of the city were flooded. Water levels rose to 2.5 metres. Zelenskyy, who had used rivers to his advantage earlier, called Russia’s move a “vile act of terror”.

The Nova Kakhovka dam disaster

Ukraine’s strategy did not end well for the country. In June 2023, it reached a devastating peak. In the early hours of 6 June, an explosion ruptured the colossal Nova Kakhovka dam built on the Dnipro River in southern Ukraine. It was a 30-metre-tall and 3.2-kilometre-long dam. Following the rupture, the dam collapsed, unleashing a torrent that swept through tens of thousands of hectares of low-lying towns, villages and farmlands.

Ukraine claimed that the dam collapse put the lives of 42,000 civilians in danger, leading to mass evacuation. Everything, including houses, bridges, and roads, was destroyed. Livestock drowned. Zelenskyy claimed that hundreds of thousands lost access to safe drinking water overnight. Around 500,000 hectares of prime farmland might turn into desert because of the disaster, experts said.

Ukraine accused Russia, which controlled the dam, of blowing it up to slow Ukrainian forces from counteroffensive across the Dnipro. Ukraine’s Foreign Minister, Dmytro Kuleba, called it a war crime of “ecocide”, citing long-term civilian and environmental damage. However, Russia categorically denied the accusations and blamed Ukraine instead. Regardless of the blame game from both sides, the result was catastrophic for Ukraine, turning the river into a weapon of mass disruption.

Turkey’s dam offensive on the Tigris–Euphrates

Not all water wars involve bombs and sabotage. Some are waged using concrete and control valves over decades. For example, Turkey used its position at the headwaters of the Tigris and Euphrates rivers to project power downstream. Its actions created chronic tensions with Iraq and Syria.

Turkey has built 22 dams and 19 hydroelectric plants across the Tigris-Euphrates basin under its ambitious Southeastern Anatolia Project (GAP). Initially, the aim was to boost irrigation and energy. However, with the vast number of dams and hydroelectric plants, Ankara now has a powerful grip over two rivers vital to its neighbouring countries.

The impact of Turkey’s control has been dramatic over the years. Ankara has the power to throttle the water flow and cause severe shortages downstream without firing a bullet. Iraq relies heavily on the Tigris and Euphrates for at least 70% of its freshwater. In recent decades, it has seen river levels plunge dramatically because of Turkey’s actions.

There are other reasons why water levels have plunged, such as climate change and drought, but Iraqi officials primarily blame Turkish dams. Research has suggested that the combined discharge of the rivers into Iraq has dropped by 50%, mostly due to upstream diversions by Turkey.

Coming to Syria, 90% of the Euphrates’ volume originates from Turkey. While Ankara claims the projects were not intended to harm anyone, it has controlled the water flow, gaining undeniable leverage. Turkey’s dam network has quietly become a slow weapon of attrition, taming rivers that once nourished the cradle of civilisation into tools of modern geopolitics.

The Nile’s dam dispute – GERD and regional fallout

Similarly, Ethiopia’s Grand Ethiopian Renaissance Dam (GERD) has become a flashpoint of geopolitical altercations between Egypt and Sudan. GERD is located on the Blue Nile near the Sudanese border and is Africa’s largest dam. It symbolises Ethiopia’s aspirations. However, for Egypt, which lies 2,500 kilometres downstream, the dam poses an existential threat. The Nile is the source of 97% of Egypt’s freshwater. The uninterrupted flow is vital for its survival.

Diplomatic efforts around GERD have repeatedly failed. Ethiopia insists it has every right to harness the Blue Nile. In 2023, it completed another phase of reservoir filling while beginning electricity generation. Egypt tried to negotiate, involving the United States and the World Bank, to reach a compromise on how quickly Ethiopia should fill and operate the dam. However, the talks failed.

Egypt believes that a rapid or unilateral fill could drastically curtail its water supply, particularly during drought years. In late 2023, when another round of negotiations failed, Egypt warned it “reserves the right” to defend its national security if harmed by GERD.

Initially, Sudan was hopeful of benefits like flood regulation. However, as time passed, it started sharing concerns with Egypt about dam safety and sudden water release risks. So far, no conflict has erupted, but that does not mean GERD cannot become another weapon of mass disruption in the 21st century.

International law against the weaponisation of water

In theory, weaponising water or manipulating rivers has no place in modern warfare. International law prohibits it. Additional Protocol I of the Geneva Conventions (1977) forbids methods of war causing “widespread, long-term and severe damage” to the environment and bars attacks on dams or dykes if such attacks could unleash dangerous forces and harm civilians.

Destroying water infrastructure to drown cities or starve populations is categorised as a war crime under international humanitarian law. On paper, these rules exist. They should prevent deliberate floods and dam bombings. However, in practice, strategic interests often override legal obligations.

Major powers have frequently ignored these laws. Neither the United States nor many other key military powers ratified Protocol I’s provisions concerning dams. In 2019, Russia, which had previously signed the document, formally withdrew its recognition of those obligations before initiating military action against Ukraine.

Conclusion

While changing river flows, stopping water, or releasing sudden influxes into rivers can be deemed as indirect warfare, weaponising water remains a significant alternative for nations seeking strategic advantage. By redirecting rivers or destroying dams, states can cripple an enemy’s food supply and economy, leading to a collapse in morale.

The damage often unfolds slowly, masked as “natural” disasters. As seen from the Indus to the Dnipro, such water wars can haveserious impact. From Alexander’s stormy crossing of the Jhelum to modern dam collapses, history shows that whoever controls the water often controls the war.

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