While conventional military forces have long been the focus of modern warfare, unconventional warfare (UW) will be waged behind enemy lines by US, allied, partner special operations forces (SOF), and civilian resistance movements. Prolonged field care (PFC) will be a forced necessity in the UW environment with unique challenges to mobility and security. Recorded experiences from World War II of allied surgeons and others reveal insights about how to prepare for this unique set of special warfare in the future, including in the areas of manning, training, planning, operations, and equipping. Countries at potential seams of conflict, like the Baltic States, possess significant UW experience. Lithuanian SOF medical leaders have developed a guerilla medicine course that increases readiness to provide PFC and austere resuscitative surgical care in UW. US military medical forces can benefit from partners like Lithuania and others by sharing knowledge, experiences, and adapting best practices to our tactics, techniques, and procedures.