enemy force may have thousands - and the trucks can be easily replaced - will represent only a minor loss on a strategic scale, but if those trucks were the only ones available to respond to a specific battle their loss could be pivotal to its outcome. Likewise, successful interdiction by blockage is even more constrained by the existence of terrain features (i.e. bridges, tunnels, etc.) upon which an enemy is dependent, and the fact that these features are often repairable or can be avoided. Destroying a bridge at the right time, if it prevents enemy reinforcements from arriving for even just a little while, might have an effect on the outcome of a battle, but on the strategic scale the enemy will be able to replace it or find an alternate route fairly shortly. In this regard, creating systemic inefficiencies in the enemy's logistical system (by using a combination of attrition and blockage on the tactical scale) has been the most successful form of strategic interdiction. An enemy that is forced to take a more circuitous route or rely on a less efficient means of transportation can, over time, find themselves falling short of their needs and so be defeated for lack of adequate supplies. Dr. Mark also identified eight conditions that affect the outcome of interdiction campaigns, the first three of which he regards as being absolutely necessary for a successful interdiction. The other five are contributory in that, while not defining all successful campaigns, at least one of the conditions was present. Air Superiority: Defined as largely unimpeded access to an enemy's airspace, air superiority is vital to a successful interdiction campaign. No interdiction campaign has succeeded where the interdictor had to fight for air superiority at the same time. Intelligence: Having sufficient intelligence of an enemy's disposition is important not only for knowing what to attack, but when and in what manner to attack them. Knowing, for example, not only an enemy's supply routes but their transportation schedule can be the difference between a successful or failed campaign. This intelligence must be constantly updated as the enemy will invariably change their methods to evade interdiction. Identifiability: If a target cannot be identified, it cannot be interdicted. This condition refers not only to the inherent nature of the target, but the surrounding environment and the level of technology involved. A convoy of ships at sea is easier