thank you so much everyone for sticking with me during 'a technical malfunction' - hopefully the gremlin has been banished. Think I'll look at re-wording. Very, very grateful - thanks to all.
Strictly, we write " The Hundred Years' War" and "the Seven Years' War" and here it should, likewise, be "two years' training". All last for a period of years; the training is of two years. If we want it adjectival we can put " two year " as an adjectival phrase.