Why did the author term the Arab army engaging the Turks as 'vaporous army'?

Directions: Answer the given question based on the following passage:

The human animal is distinguished by its constant creation of forms. Rarely expressing its emotions directly, it gives them form through language or through socially acceptable rituals. We cannot communicate our emotions without a form.
The forms that we create, however, change constantly—in fashion, in style, in all those human phenomena representing the mood of the moment. We are constantly altering the forms we have inherited from previous generations, and these changes are signs of life and vitality. Indeed, the things that don’t change, the forms that rigidify, come to look to us like death, and we destroy them. The young show this most clearly. Uncomfortable with the forms that society imposes upon them, having no set identity, they play with their own characters, trying, on a variety of masks and poses to express themselves. This is the vitality that drives the motor of form, creating constant changes in style.
Human creations evolve towards abstraction, towards being more mental and less material. This evolution is clear in art, which, in this century, made the great discovery of abstraction and conceptualism; it can also be seen in politics, which over the time have become less overtly violent, more complicated, indirect and cerebral. Warfare and strategy too have followed this pattern. Strategy began in the manipulation of armies on land, positioning them in ordered formations; on land, strategy is relatively two dimensional, and controlled by topography. But all the great powers have eventually taken to the sea, for commerce and colonization. And to protect their trading lanes they have had to learn how to fight at sea. Maritime warfare requires tremendous creativity and abstract thinking, since the lines are constantly shifting. Naval captains distinguish themselves by their ability to adapt to the literal fluidity of the terrain and to confuse the enemy with an abstract, hard-to-anticipate form. They are operating in a third dimension: the mind.
Back on land, guerilla warfare too demonstrates this evolution towards abstraction. T.E. Lawrence was perhaps the first modern strategist to develop the theory behind this kind of warfare, and to put it into practice. His ideas influenced Mao, who found in his writings an uncanny western equivalent to wei-chi. Lawrence was working with Arabs fighting for their territory against the Turks. His idea was to make the Arabs blend into the vast desert, never providing a target, never collecting together in one place. As the Turks scrambled to fight this vaporous army, they spread themselves thin, wasting energy in moving from place to place. They had the superior firepower but the Arabs kept the initiative by playing cat and mouse, giving the Turks nothing to hold on to, destroying their morale. “Most wars were wars of contact, ours should be a war of detachment,” Lawrence wrote. “We were to contain the enemy by the silent threat of a vast unknown desert, not disclosing ourselves till we attacked.”
This is the ultimate form of strategy. The war of engagement has become far too dangerous and costly; indirection and elusiveness yield far better results at a much lower cost. The main cost, in fact, is mental—the thinking it takes to align forces in scattered patterns, and to undermine the minds and psychology of the opponents. And nothing will infuriate and disorient them more than formlessness. In a world where wars of detachment are the order of the day, formlessness is crucial.