Which World War II units helped shape modern special operations warfare?

World War II served as the genesis for contemporary special operations warfare, as military forces began creating specialized units to conduct unorthodox actions behind enemy lines. Several key units from this era helped shape the modern framework of special operations:1

• Special Air Service (SAS): Formed in 1941, the SAS pioneered the concept of a strike force capable of operating independently deep behind enemy lines to attack critical targets. Its "Who Dares Wins" philosophy and focus on high-level personnel quality remain central to modern special forces.2
• British Commandos: Established in 1940, these units were designed for mobile, independent operations and deep raids along enemy-occupied coastlines. They established foundational organizational structures, such as the Special Service Brigades, and emphasized specialized training in mountain and amphibious warfare.3
• Office of Strategic Services (OSS): This U.S. agency focused on intelligence gathering, sabotage, and supporting resistance movements. Its diverse functions in espionage and unconventional warfare laid the groundwork for the modern Central Intelligence Agency.45
• Other Specialized Units: Forces such as the joint U.S.-Canadian First Special Service Force, the German K-Verband combat swimmers, and the Italian Decima Flottiglia MAS demonstrated the effectiveness of specialized naval and mountain assault teams, influencing the evolution of permanent special forces capabilities.1