What qualifies as "terrorism" is a semantic and emotionally freighted question which only obscures the more important inquiries of whether, and under what circumstances, we are willing to tolerate acts of warfare which, either by design or as unavoidable consequence, will inflict death and suffering on what are generally termed "civilians". I doubt a war has ever been fought in which the combatants have assigned a higher priority to avoidance of likely civilian carnage than to attaining their war aims. The analysis is complicated by the fact that warfare can rarely be conducted with much effect in the absence of a significant, supportive civilian population. One might even ask whether there is much of a moral distinction to be drawn between combatants, on the one hand, and civilians who put war governments in power, manufacture armaments, feed armies, harbor suicide bombers, etc.
Ultimately, it is only the old question of ends and means, with the balance weighed by the victor.