The canonicity of Vikings is up in the air, as I do not believe there is anything that explicitly confirms if it's canon or non-canon... And because some MAX titles are canon and some are not, the series can't be ruled in or out that way either.
"A great tactician creates plans.
A good tactician recognizes the soundness of a plan presented to him.
A fair tactician must see the plan succeed before offering approval.
Those with no tactical ability at all may never understand or accept the plan.
And when a mind is too deficient in understanding, the resulting gap is often filled with resentment."