The advent of nuclear weapons heralded a fundamental shift in warfare, as war for the first time confronted humanity with the prospect of complete annihilation. Military and civilian strategists sought avenues for fighting and competing without triggering a nuclear holocaust, which led nations to moderate their ambitions and settle for outcomes short of victory. This change in strategic calculus is the primary, although not the only, reason why wars have been more difficult to win since 1945.
In the first two major wars after World War II, the fear of nuclear war, in combination with the fear of protracted warfare inside China, discouraged the United States from taking actions necessary for decisive victory. When the Chinese army intervened in the Korean War, Douglas MacArthur urged President Truman to invade China and strike it with nuclear weapons to obtain a decisive victory. Truman, however, feared that MacArthur’s proposed strategy would provoke a nuclear response from China’s Soviet ally and bog the United States down on the Chinese mainland. As a result, Truman chose to keep the war within the confines of the Korean peninsula, producing a military stalemate that ended with a peace agreement leaving neither side victorious.
During the Vietnam War, top U.S. military leaders urged President Lyndon Johnson to invade North Vietnam and smash it with air power to end the war. Johnson rejected their advice, believing that these actions would lead to a third world war against China, which by then had nuclear weapons of its own. Hence, the United States remained on the strategic defensive, and eventually it lost the will to continue bankrolling its South Vietnamese allies.
During the war in Afghanistan of 2001–21, Pakistan’s possession of nuclear weapons discouraged the United States from violating Pakistan’s sovereignty to the extent necessary to deprive the Taliban of access to Pakistani territory. The sanctuary afforded by Pakistan enabled the Taliban to keep fighting in Afghanistan regardless of casualties. Losing patience with protracted conflict again, the United States would abandon its allies once more.
When Russia invaded Ukraine in 2022, it stood a good chance of achieving decisive victory, because Ukraine had unilaterally relinquished its nuclear weapons in 1994 based on ephemeral foreign security guarantees. But Ukraine’s conventional forces foiled the Russian military’s attempts to seize Kiev. During the ensuing stalemate, fear of a global nuclear war has prevented both Russia and Ukraine’s allies from using nuclear weapons in pursuit of total victory.
In recent insurgencies and civil wars, as in more distant ones, poor leadership has often prevented victory. Great powers seeking to maintain a friendly government often prop up weak leaders, because of either deference to national sovereignty or a lack of good alternatives, and many such leaders prove incapable of completely eliminating enemy combatants within their own borders. The United States was saddled with this problem in Cambodia, El Salvador, Somalia, Iraq, Afghanistan, and Yemen. The Soviet Union faced the same problem in Afghanistan and Ethiopia. Other examples include Yugoslavia in Greece; South Africa in Angola; France in Indochina; and Britain in Yemen.
Heightened aversion to large and persistent casualties has also curbed the appetites of some nations for the protracted attrition warfare that led to decisive outcomes in the past. This aversion contributed to American willingness to end many of its recent wars without victory: the Korean War, the Vietnam War, the Somalian intervention, the Iraq War, and the Afghanistan War. European nations repeatedly gave up on post-1945 wars that accrued too many casualties, such as the First Indochina War, the Algerian War, and the Troubles.
Greater media coverage of war has contributed to this aversion. So has the decline in family size. When the average family had three or four sons, it was more accepting of the risks of sending a son into the military than in the current epoch, when few families have more than one son. The spread of democracy has also contributed, for democratic nations are more responsive to the sentiments of the masses whose sons make up most of the armed forces. In addition, decline in religious belief in parts of the West has intensified casualty aversion, since humans are generally less willing to risk their lives if they do not believe in anything beyond the current world.
