Historically, conventional wars between states fighting for sovereignty peaked between the seventeenth and eighteenth centuries, while national wars rose to prominence from the Napoleonic Wars at the start of the nineteenth century until the end of World War I. Other forms of warfare include the horrendous religious wars, which have long been overcome, and unconventional warfare (UW), which spawned a lot of variation since emerging and becoming a popular mode of stirring up chaos amid the Second World War into the Cold War era, evolved significantly through the twenty-first century. The latter has become a preferred mode fought by mercenaries, insurgents, subversives, guerrillas, special force units, and sometimes for-hired or for-a-cause assassins. Occasionally it can be fought directly through infiltration and raids, and other times indirectly, such as political and economic sabotage, espionage, and orchestrating an uprising behind closed doors—UW has spawned many variations of its own, which drastically evolved since the turn of the twentieth century.

But why has it grown in popularity? For one, UW has proven to be a viable, most cost-effective indirect action method that has aided superpowers in achieving their tactical objectives in the last few decades.

Below are some popular classic unconventional tactics used by Western militaries throughout history.


Among the most common and popular forms of unconventional warfare is espionage, typically used by Britain’s Secret Intelligence Service (also known as MI6).

By definition, espionage is obtaining top-secret intelligence by employing undercover agents and spies or using covert gadgets such as “bugs” and monitoring/listening devices that are usually considered illegal.

This unconventional tactic commonly occurs in foreign territories where a suspecting nation wants to uncover confidential, potentially sensitive information that may or may not threaten the latter.

As mentioned, Britain’s MI6 is one of the agencies charged with utilizing espionage, which has been believed to have existed since the 1500s. It was formally constituted in the early 1900s, just a few years before the First World War broke out. The covert human intelligence gathering grew during the rise to power of the Third Reich – operating across Europe, Latin America, and Asia.

Madame Minna Craucher (right), a Finnish socialite and spy, with her chauffeur Boris Wolkowski (left) circa 1930s. (Image source: Wikimedia Commons)

The United States also formed its version of the British Secret Service when it joined World War II, with the MI6 training American personnel under the Office of Strategic Services (OSS)—later succeeded by Central Intelligence Agency (CIA).