I have two theories as to why this connection might be:
1. Celtic/folk music has more songs about soldiering and war than popular music does. Turn on any radio station today (regardless of the genre) and you’re unlikely to hear a song about war or the soldier’s life. Sure, there are some, especially in the country music genre, but most songs today are about romantic love. Romance is great, but one of the things people often look for in art is a reflection of themselves, something to help them express their feelings, etc. Some servicemen and servicewomen may turn to Celtic/folk music because the age-old experience of the soldier takes centre-stage in many folk songs, for example “The Recruiting Seargent,” “Johnny, I Hardly Knew Ye,” “Will Ye Go to Flanders?” and “No Man’s Land.”
2. The armed forces place a great emphasis on tradition. From their flags and insignia, to their mottos and uniforms, the military often places a great importance on being part of a tradition. This also includes remembering and honouring the fallen. Part of this culture can include preserving old songs of war, and, more broadly, the body of traditional folk music to which they belong. Soldiers risk their lives for their country, and it seems that being part of a long and proud tradition can help them understand their role. Again, I’ve never served, but the theory seems to make sense. Military members may join a regiment and get their first exposure to these Celtic songs over a shared beer in company of those who will serve with them. Folk music can then become a living part of the traditions that they carry on.
So, these are my theories as to the link between military service and Celtic/folk music. I’ve been grateful for the warm support I’ve received from veterans and active military folk both in person and online. If you’ve served and have some insight into this link, please do add your thoughts in the comments section. And thanks for your service!