In 1941, Mr Donaldson revealed to a close confidant - who was also a British agent - that a network of Nazi sympathisers were planning to undermine the war effort.
Mr Donaldson told the agent that he believed the German invasion would be a success.
"The government would leave the country and England's position would be absolutely hopeless, as poverty and famine would be their only reward for declaring war on Germany. Scotland, on the other hand, has great possibilities," Mr Donaldson is recorded as saying.
"The movement in Scotland must then be able to show the German government that it is organised and has a clear-cut policy, that it is not with England in the war.
"The German government will give them every possible assistance in their early struggle, and when fire and confusion is at its height in England the movement can start in earnest."
Senior MI5 officer Lieutenant Colonel Dick Brooman-White believed that Mr Donaldson was planning to follow the lead of Vidkun Quisling, who led a puppet government in Norway.
In 1941 Mr Donaldson was among a number of Nationalist figures to be arrested under suspicion of subversive activities.
It's a shame he wasn't hanged for treason.
You cannot negotiate with those who want you dead.