2. The purpose of a military campaign is to achieve a particular desired resolution of a military conflict as its strategic goal. This is constrained by resources, geography and/or season. A campaign is measured relative to the technology used by the belligerents to achieve goals, and while in the pre-industrial Europe was understood to be that between the planting (late spring) and harvest times (late autumn), it has been shortened during the post-industrial period to a few weeks. However, due to the nature of campaign goals, usually campaigns last several months, or up to a year as defined by Trevor N. Dupuy.