Canada: https://en.wikipedia.org/wiki/Commander-in-Chief_of_the_Cana...
As all executive power is legally reposed in the Crown, the role of commander-in-chief is the only constitutional means by which decisions are made over the deployment and disposition of the Canadian Armed Forces.[6] Under the Westminster system's conventions of responsible government, the cabinet—which advises the sovereign or his viceroy on the exercise of the executive powers—generally exercises the Crown prerogative powers relating to the Canadian forces.[6][7] Still, all declarations of war are issued with the approval, and in the name, of the monarch and must be signed by either the sovereign or the governor general, as was done with the proclamation that declared Canada at war with Nazi Germany, issued on September 10, 1939; it stated: "Whereas by and with the advice of Our Privy Council for Canada, We have signified Our Approval for the issue of a Proclamation in the Canada Gazette declaring that a State of War with the German Reich exists and has existed in Our Dominion of Canada as and from the tenth day of September, 1939."
Australia: http://classic.austlii.edu.au/au/legis/cth/consol_act/coaca4...
COMMONWEALTH OF AUSTRALIA CONSTITUTION ACT - SECT 68.
Command of naval and military forces.
The command in chief of the naval and military forces of the Commonwealth is vested in the Governor-General as the Queen's representative.