I think they join for all the wrong reasons, for power, for purpose and for money.
The last serious attempt to win over soldiers got the whole of the Communist leadership in prison back in 1925 for incitment to mutiny. The conditions for winning over potential or serving soldiers is very slender in the present conditions. They are, at heart, loyal to each other and to the forces - it would take more that the present state of the left to change that - as anyone involved in Irish politics will know only too well. I'm aways amazed at the lack of fightback from the families of soldiers when the kids are killed or injured or abused by officers.
My view is that when the conditions arise for an army to split it won't take people from outside to make it happen, I'm sure they will manage to do it themselves.
I'm far more concerned with the victims of British foreign policy than the poor individuals who continue to sign-up to fight for Queen & Country.