Falklands was invasion of territory so 'War' is appropriate as a sovereign nation was the on other side of the conflict as agressor.
It was 'Argentina' v 'UK'
We did not go to war against 'Afghanistan'
Did we go to war against 'Iraq' ? Or was our invasion an act of war?
An mentioned above the diplomacy is vital so 'War' or not in Falklands was a balancing act.
Simliarly no 'War' in NI as that would have repurcussions .