The contribution of actual (rather than potential) military force to strategy was largely reduced to operational strategy - the planning and control of large military units. Rome's grand strategy incorporated diplomacy through which Rome might forge alliances or pressure another nation into compliance, as well as the management of the post-war peace. Vegetius wrote that "every plan... is to be considered, every expedient tried and every method taken before matters are brought to this last extremity [general engagements]... Good officers decline general engagements where the odds are too great, and prefer the employment of stratagem and finesse to destroy the enemy as much as possible... without exposing their own forces.". However, Vegetius was writing late in the fourth century AD, in the latter years of the Empire. During this period, and for much of the Empire, it can be argued that the Romans did follow a grand strategy calling for limited direct operational engagement. However, earlier in its history, in the Republic and early Empire Rome showed little reluctance to become engaged in direct military engagement, prosecuting offensive operations against numerous adversaries. When a campaign did go badly wrong, operational strategy varied greatly as the circumstances dictated, from naval actions to sieges, assaults of fortified positions and open battle. However, the preponderance of Roman campaigns exhibit a preference for direct engagement in open battle and, where necessary, the overcoming of fortified positions via military engineering. The Roman army was adept at building fortified camps for protection from enemy attack, but history shows a reluctance to sit in the camp awaiting battle and a history of seeking open battle. Roman armies of the Republic and early empire worked from a set tactical 'handbook', a military tradition of deploying forces that provided for few variations and was ignored or elaborated only on occasion. Once the legion had deployed on an operation, they would generally march to their objective. There were exceptions when the armies were transported by the Roman navy but even then in most instances this was followed by a march of several days or weeks. The approach to the battlefield was made in several columns, enhancing maneuver. Typically a strong vanguard preceded the main body, and included scouts, cavalry and light troops. A tribune or other officer often accompanied the vanguard to survey the terrain for possible camp locations. Flank and recon elements were also deployed to provide the usual covering security. Behind the vanguard came the main body of heavy infantry. Each legion marched as a distinct formation and was accompanied by its own baggage train. At the end of a day's march, the Romans would typically establish a strong field camp called a castra, complete with palisade and a deep ditch, providing a basis for supply storage, troop marshalling and defence.