Well, the dictionary difference is quite simple - a partisan/guerilla is fighting against an occupying power...whereas an "insurgent" is rebelling against his "own government" or ruling political party. Therefore its NOT defined by the person themselves or their actions, but relative to who they're fighting.
And - of course - by who's looking from the outside in
The Maquis and others in France would be insurgents to the German point of view, and to the Vichy government - legally speaking....
But to the Free French abroad they'd be partisans. Depends on who's describing them...and whether they see
themselves as an occupying force - or after armistice and surrender - the "legitimate" government.
A fine point to argue, but real nonetheless. As it THEN begs the question of...which is the
legitimate government...a tiny fraction of the French armed forces and escpaed civilian government abroad - or the German government of occupation and Vichy Regime AFTER official agreement (surrender) with the previous French government at Compiegne.
Like so many things - it depended which retrospective point of view was there as of May 1945 to judge.
"Well, my days of not taking you seriously are certainly coming to a middle." - Malcolm Reynolds