When planning for any kind of undertaking outdoors, but especially for escape and evasion, it is essential to consider how weather, terrain and human factors will impact oneself, the members of one’s group, equipment used and the ability to accomplish the intended objective. In the case of avoiding potentially hostile encounters, it is also important to take into account the effects that weather, terrain and human considerations will have on any pursuers or adversaries.
With other more poetic words, we could describe this as figuring out how to harmonize and fit in with what has been called the law of heaven, the scheme of totality or simply the way the universe is and how it operates.
To this end, the present article deals with the analysis of weather and its effects, while terrain and human considerations are addressed in other articles. This is not a survival guide for all types of weather conditions, but merely an attempt to outline the main basic points to be taken into account.
Tenton Jūppō (天遁十法, “Ten Heaven Methods of Escaping/Disappearing”)
Such a three-fold set of considerations as described above is reflected in the thirty ongyōjutsu (隠形術, “hidden forms methods”) attributed to the Japanese ninja, namely, the tenchijin santon no hō (天地人三遁の法, “heaven, earth, man-three methods of escaping”). Divided into three sets of ten, respectively associated with heaven, earth and man, the first set is known as tenton juppō (“ten heaven methods of escaping/disappearing”). It includes nitton (日遁, “sun escape”), getton (月遁, “moon escape”), seiton (星遁, “stars escape”), unton (雲遁, “clouds escape”), muton (霧遁, “fog escape”), raiton (雷遁, “thunder escape”), denton (電遁, “lightning escape”), fūton (風遁, “wind escape”), uton (雨遁, “rain escape”) and setton (雪遁, “snow escape”).[1]
The Five Military Aspects of Weather
Modern militaries also regard weather factors as a crucial fundamental consideration, such as in terms of the five militarily significant aspects of weather: visibility, wind, precipitation, clouds and temperature/humidity. These five aspects guide the remainder of the discussion in this article.
Overall, the impact of weather on oneself is generally more immediate than its impact on one’s equipment and supplies. Differences between individuals, such as resulting from physical fitness level, can make one person more or less able to adapt to certain weather conditions. Whatever the case, extreme temperatures are the most consequential weather factor in terms of direct impact on human beings. This factor is discussed last. It is also important to note that these five aspects interact with one another and different conditions can have similar effects. For instance, various inclement weather conditions, such as pertaining to visibility, precipitation, winds, lightning and temperature can inhibit search and rescue aircraft. Moreover, the different aspects of weather also interact with characteristics of the terrain. For example, the interaction of topography and air flow can lead to potentially compromising scents travelling great distances or settling in low-lying areas
Visibility:
Visibility factors in solar and lunar light data; namely the times for BMNT, sunrise, sunset, EENT, moonrise and moonset, along with the moon’s percentage of illumination. Moreover, positioning of the sun in relation to oneself as well as pursuers or potential adversaries is also important, with it being far better to have the sun in the opponent’s eyes and to one’s own back.
But it is also crucial to consider the presence or absence of any obscuring factors like fog, smog, smoke and dust, as well as various forms of precipitation, like rain, snow, sleet and hail, not to mention their relation to the next consideration of wind.
Whatever the weather situation, it is important to consider its impact on the enemy’s ability to see oneself, as well as vice versa, along with how one may capitalize on this situation to accomplish one’s objective.
Wind:
In conventional military terms, being upwind in relation to one’s enemy is generally more advantageous because of better visibility for oneself and worse visibility for the enemy. This relates to how the wind itself, along with any dust, sand, precipitation, etc., is blowing into the enemy’s eyes when they are oriented to observe one’s position.
Yet pertaining to stealth for the purposes of escape and evasion, since the objective is not “to close with and destroy the enemy,” this advantage of having the wind in the opponent’s eyes mostly applies to the initial escape or to escaping from any subsequent unavoidable close encounters.
Ideally, once contact has been broken, one uses the available terrain, vegetation and manmade structures for concealment and camouflage. This allows for a more subtle use of wind direction, namely, pertaining to audial and olfactory target indicators. Both sound and scent can be carried further distances by wind. Thus, after contact has been broken, while relying on effective camouflage and concealment to avoid visual detection during evasion, one remains upwind of hostile observers to prevent any sounds or scents that one may produce from being carried by wind to the enemy.
So the lesson here is: When initially escaping, run into the wind if possible, but while evading, remain upwind of the area you have assessed the enemy is likely to be.
Another important factor regarding wind and stealth is that the sound produced by wind can mask one’s own movements, but it can also mask the movements of one’s adversaries.
Wind direction is something that can change quickly and it must thus be continuously monitored. It can be determined by wetting one’s finger and noting which side is coolest, tossing vegetation up in the air and observing how it falls or, in stronger winds, observing the direction in which grass, bushes or tree branches are being blown.
Yet beyond avoiding detection, wind also has an important effect to consider on the body’s thermoregulation: Wind can cause greater heat loss from exposed skin, thus making the air feel colder but also reducing one’s body temperature. This is known as wind chill. In cold or even moderate weather environments, such heat loss can be dangerous, possibly leading to hypothermia and/or frostbite.
Lastly, it should also be noted that strong winds make negotiating steep terrain or climbing particularly hazardous. This is not to mention the risk of falling trees or branches along with the possibility of wind damaging signal towers and thus affecting communications.
Precipitation:
Key facets to consider with regard to precipitation are its type, amount and duration, along with its effects on visibility, thermoregulation, equipment (including especially communications) and trafficability.
Large amounts of precipitation and/or precipitation blown in the direction of the observer reduce visibility.
Pertaining to thermoregulation, being wet promotes heat loss, which can be detrimental in even moderate conditions. Thus, it is imperative to remain dry. But there are also other preventative medicine reasons for remaining dry, such as avoiding “trench foot.”
Measures must also be taken to ensure that personal equipment and supplies are kept dry. A wet paper map, for instance, can quickly become unusable. Precipitation can also adversely affect the operation of communications equipment, for example, degraded GPS or mobile phone reception.[2]
Soil trafficability (in vehicles or on foot) can be adversely affected by precipitation, such as by making terrain muddy, snow-covered or slippery, especially when combined with freezing temperatures. Precipitation can also make tracks left behind more noticeable, or conversely, it can facilitate silent movement by moistening dry vegetation. Like wind, the sound of falling precipitation itself can also mask movement.
Cloud Cover:
Cloud cover can prevent one from being able to see the sun, moon and stars, thus inhibiting one’s ability to carry out celestial navigation.
Pertaining to visibility, a cloudy sky makes for a darker night in rural settings, since it prevents moonlight from illuminating the environment, while in urban settings the opposite is true and cloudy nights are brighter, since they reflect and even amplify city lights.[3]
Additionally, like precipitation, clouds too can adversely affect GPS signal and mobile phone reception. Lastly, the risk of lightning strikes associated with storm clouds is a serious safety concern.[4]
Yet it is not only the presence of clouds that must be considered, but also the lack thereof. The absence of cloud cover of course facilitates celestial navigation.
Moreover, direct sunlight unimpeded by such cloud cover has a number of effects, both positive and negative. It can contribute to sustaining sunburn as well as hot weather injuries.
More positively, the direct sunlight allowed by a lack of clouds also facilitates the use of mirrors or other reflective surfaces for signaling or eyeglasses, magnifying glasses, etc. for fire-starting.
Pertaining to stealth, direct sunlight creates greater contrast, making darker shadows to hide in. As mentioned above, having the sun shining in the observer’s eyes also facilitates stealth.
Temperature/Humidity:
Extreme temperatures, whether high or low, are the single most important factors to consider in terms on their effect on human beings.
Low temperature effects on humans
Low temperatures come with the risk of cold weather injuries like frostbite, hypothermia, chilblain and trench foot. A helpful acronym outlining key preventative medicine points for operating in low temperatures is COLD:
-Keep clothing Clean,
–Observe each other for signs of cold weather injuries, or avoid Overheating (because of too much clothing, especially when exerting oneself)
-Wear Loose layers of clothing, and
-Stay Dry
Because of physical exertion in heavy clothing along with the typically dry air, cold temperatures can increase the need for water consumption. Yet the availability of water is limited in subzero temperatures (Celsius) due to freezing.
High temperature effects on humans
As mentioned above, the temperature combined with wind speed determine the wind chill, which can increase the risk of cold weather injuries. Similarly, high temperatures, especially in conjunction with high humidity, increase the risk of hot weather injuries like heat exhaustion and heat stroke.
It is crucial to ensure sufficient water consumption in warm weather conditions. Electrolytes, particularly sodium, should also be replenished to replace those lost through sweating.
Likewise, it is necessary to pace oneself and incorporate rest periods while carrying out any tasks requiring physical exertion.
Extreme temperature effects on equipment
Vehicles and other equipment are more prone to overheating in hot weather conditions, while in extreme cold, they may also fail to work properly. The latter case is especially true of battery-operated equipment, since batteries produce less electrical current in the cold.
Regarding freezing temperatures, depending on the terrain, trafficability in vehicles or on foot can be helped, by making muddy ground harder, or hindered, by creating slick frozen surfaces.
Stealth, temperature and humidity
Pertaining to how temperature and humidity affect stealth and the perceptibility of audial recognition factors, cooler temperatures are more conducive to the propagation of sound, while warmer temperatures are less so. Similarly, lower humidity is more conducive to sound propagation, while higher humidity is less so. Thus, it is easier to hear or be heard in cold and/or dry conditions, while it is harder to hear or be heard in hot and/or humid conditions.
The perceptibility of olfactory recognition factors is also affected by temperature and humidity. Warmer temperatures are conducive to smell while coolers temperatures have the opposite effect. Likewise, higher humidity is more conducive to smell than lower humidity.
Bibliography
Centers for Disease Control and Prevention. “Lightning Safety Tips.” CDC.gov. https://www.cdc.gov/disasters/lightning/safetytips.html (accessed 17 July 2021).
Itoh, Gingetsu. Gendaijin no Ninjutsu. Trans. Eric Shahan. Charleston: CreateSpace, 2014.
Itoh, Gingetsu. Ninjutsu no Gokui. Trans. Eric Shahan. Charleston: CreateSpace, 2014.
Public Library of Science. “Clouds Amplify Ecological Light Pollution.” ScienceDaily, www.sciencedaily.com/releases/2011/03/110302171312.htm (accessed July 17, 2021).
Siler, Wes. “How Weather Affects Your Cell Signal: Using a Phone Outdoors? This is What You Need to Know to Stay in Touch.” OutsideOnline. https://www.outsideonline.com/outdoor-gear/tools/how-weather-affects-your-phones-signal/ (accessed July 17, 2021).
Tanemura, Shoto. Ninpo Secrets: Philosophy, History and Techniques, 3rd Ed. Matsubushi, Japan: Genbukan World Ninpo Bugei Federation, 2003.
U.S. Department of the Army. Battlefield Weather Effects. Field Manual 31-81-1. Washington, DC: Headquarters, Dept. of the Army, 1992.
U.S. Department of the Army. Infantry Platoon and Squad. ATP 3-21.8. Washington, DC: Headquarters, Dept. of the Army, 2016.
[1] See, for example, Shoto Tanemura, Ninpo Secrets: Philosophy, History and Techniques, 3rd Ed. (Matsubushi, Japan: Genbukan World Ninpo Bugei Federation, 2003); Gingetsu Itoh, Gendaijin no Ninjutsu, Trans. Eric Shahan (Charleston: CreateSpace, 2014) ; Itoh, Gingetsu, Ninjutsu no Gokui, Trans. Eric Shahan (Charleston: CreateSpace, 2014).
[2] Wes Siler, “How Weather Affects Your Cell Signal: Using a Phone Outdoors? This is What You Need to Know to Stay in Touch,” OutsideOnline, https://www.outsideonline.com/outdoor-gear/tools/how-weather-affects-your-phones-signal/ (accessed July 17, 2021).
[3] Public Library of Science, “Clouds Amplify Ecological Light Pollution,” ScienceDaily, www.sciencedaily.com/releases/2011/03/110302171312.htm (accessed July 17, 2021).
[4] For lightning safety tips, both indoors and outdoors, see: Centers for Disease Control and Prevention, “Lightning Safety Tips,” CDC.gov, https://www.cdc.gov/disasters/lightning/safetytips.html (accessed 17 July 2021).