The PMESII-PT Model

As with any complex situation, the factors of the PMESII-PT construct will vary in priority depending on the operational environment. Two factors I believe are critical regardless of the environment are the Political and Physical Environment variables of the construct.
To begin with, the Political element of the PMESII-PT model focuses on the distribution of power and responsibility in a particular region, to include formal governmental institutions and tribal hierarchies. This element includes factions that might hold political sway in the region, like opposing parties and informal organizations. Before commanders can safely navigate the treacherous waters in a politically unstable region, they must consider which parties or factions have the perceived legitimacy to the populace, and how those parties feel toward the United States. An excerpt from FM 1-01 identifies the criticality of examining the political climate at the local, regional, and national levels for the commander to
Commanders must be familiar with the terrain upon which their units will be operating, because that knowledge will determine the type of equipment the units must be able to operate. Will they require wheeled or track vehicles? Is there an abundance of land mines or other obstacles that would require clearing before the units occupy the area? Are there mountains or waterways that would require special equipment to traverse? Commanders must also be knowledgeable about weather trends and vulnerabilities specific to the region. Is the unit going to be occupying the area during a particularly rainy season, or is the area susceptible to drought, or significant temperature fluctuations between day and night? Is it in an area prone to earthquakes, volcanic activity, or tidal events? Commanders must consider all these factors in order to most effectively equip, prepare, and acclimate their