Nationalisation as a Military Seizure

Did Britain and France first turn the canal dispute into a military affair?

No: Egyptian troops enforced the takeover by removing the company’s foreign administrators.

Nasser's nationalisation involved Egyptian troops ejecting the British and French administrators of a civilian-run company. The canal organisation was not itself a military command, so soldiers enforcing the takeover changed the character of the dispute. That coercive act helps explain why Britain and France treated nationalisation as more than a commercial disagreement. It does not justify the later invasion by itself, but it complicates the claim that only the European powers introduced force into the crisis.