At least 12 killed after Thailand launched airstrikes on Cambodia

On July 23, Thailand carried out airstrikes on Cambodian military positions near their long-disputed border, intensifying already high tensions between the two Southeast Asian nations. In response, Cambodia vowed to “respond decisively.” Just hours earlier, clashes between Thai and Cambodian forces erupted in several border areas. According to the Thai army, Cambodian attacks have killed at least 12 people so far and injured more than a dozen in Thailand, including an eight-year-old boy.

The escalation followed an incident the previous day in which a Thai soldier lost a leg to a landmine near the border. The blast triggered a sharp deterioration in diplomatic relations, with both Bangkok and Phnom Penh downgrading ties to their lowest point in years.

The Thailand–Cambodia conflict is one example of how long-standing rivalries between nations can spiral into violence. Across the world, historical disputes, border disagreements, and political tensions have fueled some of the most enduring international rivalries.

So, which countries have the greatest rivalries? Click through and read about the issues dividing these nations.

Israel–Iran

There weren’t always ongoing hostilities between Iran and Israel. In 1948, Iran was the second Muslim-majority country that came to recognize Israel after it was founded in 1948. However, things turned sour when Mohammad Mosaddegh became Iran’s prime minister in 1951. He cut ties with Israel, believing that Israel was supportive of Western interests in the Middle East region. When a coup orchestrated by the intelligence services of the UK and the US prompted the overthrow of Mosaddegh and the reinstating of a pro-West shah, relations between the countries improved once again.

Iran–Israel

Then the Iranian Revolution took place in 1979, prompting another change in government. The focus of Iran’s leaders shifted to championing Islam and supporting Palestine, which brought on the changes in attitude towards Israel. Today, Israel and Iran are locked in what has been dubbed as a "shadow war," instigated by clashes in ideologies, such as Israel’s firm opposition to Iran developing nuclear weapons. Tehran, on the other hand, further advocates that it aims to continue with its nuclear program for civilian purposes.

Germany–France

These two powerhouse European nations have not always been the best of neighbors, their shared border providing a conduit for numerous conflicts, among them Napoleon's victory against Prussia in the War of the Fourth Coalition, and the Franco-Prussian conflict that resulted in a win for Germany.

France–Germany

France's blaming of Germany for the First World War in the Treaty of Versailles exacted a terrible revenge from Nazi Germany. Hitler occupied the country for most of the Second World War and quite literally divided a nation. Today, relations between France and Germany are warm and constructive with both among the most enthusiastic proponents of the further integration of the European Union.

China–Japan

The rivalry between China and Japan is as ancient as their lands. The first recorded battle between China and Japan took place in 663, the Battle of Baekgang, with Imperial China the victor. More recently, grievances still fester over Japan's reluctance to fully acknowledge war crimes committed during the Second Sino-Japanese War and throughout the Second World War.

United Kingdom–Ireland

The sovereign state of the United Kingdom of Great Britain and Ireland existed between 1801 and 1921. However, a strong desire for Irish independence led to the Easter Rising of 1916 and later the Irish War of Independence, fought between 1919 and 1921. The formation of the Irish Free State in 1922 eased tensions somewhat between London and Dublin, but excluded an area known today as Northern Ireland.

Israel–Palestine

Arguably the most complex, divisive, and destructive nation relationship in the world is that of Israel and Palestine. The bad blood that exists between these two states can be traced back to 1917 and the British Mandate for Palestine. During the mandate, the area saw the rise of nationalist movements in both the Jewish and Arab communities. The termination in 1947 of the mandate and the creation of the State of Israel sparked what has become known as the Israeli–Palestinian conflict—one of the world's most enduring geopolitical disputes and one that has expanded into a wider Arab-Israeli conflict.

Turkey–Greece

The relationship between Turkey and Greece is long and complex. The roots of their rivalry were planted in the 15th century with the annihilation of the Byzantine Empire by the Ottoman Empire in 1453. Despite its independence being recognized in 1832 by the Ottoman Empire, the newly established Kingdom of Greece and the Ottomans would battle it out through various conflicts fueled by nationalism until the end of the First World War. Even after the dissolution of the Ottoman Empire and the founding of Turkey in 1923, the two nations found time to clash heads again, this time over Cyprus.

Greece–Turkey

Today, geopolitical issues still strain the relationship between the two countries. The Aegean dispute is an especially thorny issue, with Greece and Turkey hankering over sovereignty and related rights in the region of the Aegean Sea since the 1970s. Indeed, the conflict has twice led to crisis coming close to the outbreak of military hostilities, in 1987 and 1996.

North Korea–South Korea

Korea was once a single nation but was annexed by Japan in 1910. The Korean Peninsula has been divided into North Korea and South Korea since the end of the Second World War in 1945, demarcated by the infamous 38th parallel. The North was supported by the Soviet Union while the United States backed the South.

India–Pakistan

Relations between India and Pakistan have been complex and largely hostile since the violent partition of British India in 1947 and the founding of the Islamic Republic of Pakistan the same year. The subsequent years have seen numerous military conflicts fought between the two nations.

United Kingdom–France

Conquest, wars, and alliances at various points in history typify the long and complex relationship between the United Kingdom and France. Throughout the Middle Ages, France and England were often bitter enemies, the Norman conquest of 1066 being one of the most decisive and consequential victories over England in the medieval period. The last major conflict between the two countries were the Napoleonic Wars (1793–1815). The late 19th century saw rivalry develop between France and England for African colonies, but by 1904 the Entente Cordiale signaled warmer ties between the once warring nations.

Iran–Saudi Arabia

Near neighbors Iran and Saudi Arabia are two of the Middle East's most powerful countries. Their relationship with one another, however, is fraught and contentious. While both are Islamic nations, Saudi Arabia is a conservative Sunni absolute monarchy, while Iran is a mostly Shia republic.

Kuwait–Iraq

Historically, most of present-day Kuwait was part of ancient Mesopotamia, a region that today occupies modern Iraq. Pre-oil Kuwait was a strategic trade port between Mesopotamia, Persia, and India. Oil reserves were discovered in commercial quantities in 1938. Kuwait formally gained independence in 1961, though Baghdad initially refused to recognize the fact by maintaining that Kuwait was part of Iraq. In 1963, however, a treaty of friendship between the two countries was signed by which Iraq formally recognized the border separating it from its neighbor.

Albania–Serbia

Distrust and animosity are the bywords that best describe the nature of the historical relationship between these two Balkan states. After the defeat of the Ottomans in the Balkan Wars of 1912–1913, the modern nation state of Albania declared independence in 1912. Numerous war crimes were committed by all parties engaged in the conflict, though Serbia's treatment of the Albanian population was particularly brutal.

Armenia–Azerbaijan

The ongoing Nagorno-Karabakh conflict, an ethnic and territorial squabble between Armenia and Azerbaijan over the disputed region of Nagorno-Karabakh, inhabited mostly by ethnic Armenians, has stymied all attempts to forge diplomatic relations between these two neighboring Western Asian states.

Chile–Peru

These two South American nations had enjoyed peaceful and productive relations dating back to the Inca Empire in the 15th century, a bilateral partnership that was further strengthened after both became independent from Spain in the 19th century. But that all changed with the outbreak in 1879 of the War of the Pacific.

Peru–Chile

The War of the Pacific pitted Chile against a Bolivian-Peruvian alliance and was fought over Chilean claims on coastal Bolivian territory in the Atacama Desert. A Chilean victory brought with it a significant amount of resource-rich territory from Peru and Bolivia. The result of the five-year conflict soured relations between the two countries for over a century, with their bond further tested in 1975 when left-wing Peru and right-wing Chile were again on the brink of war. Today, relations have greatly improved.

Kenya–Somalia

Tensions between these two East African nations have simmered since the early 1960s when both countries gained their independence. The Shifta War (1963–1967) saw ethnic Somalis in the northern frontier district of Kenya attempting to join Somalia. Despite a 1967 ceasefire, sporadic violence in the region continued for several decades.

Somalia–Kenya

In fact, both sides have been embroiled in border disputes, petty skirmishes, and in some cases bloody massacres. In 2021, ties between the two countries fell to a historic low when Mogadishu cut off diplomatic relations and accused Nairobi of meddling in its internal affairs. Compounding this mutual intransigence is the Dadaab refugee crisis. Dadaab is one the world's largest refugee camps and home to thousands of displaced Somalis. Kenya wants to shut it down and has given the UN until June 2022 to find a new home for most Somali refugees. The two nations are also engaged in a long-running maritime territorial feud across the Indian Ocean believed to hold valuable oil and gas reserves.

Thailand-Cambodia

Thailand and Cambodia share a 508 mile (818 kilometer) border that has long been a source of tension, with periodic clashes rooted in unresolved territorial disputes. The boundary, originally drawn during French colonial rule in Cambodia, remains contested—especially near ancient temple sites.