These general principles in the art of war were entirely unknown, or
lost sight of, in the middle ages. The crusaders in their incursions
into Palestine appear to have had no object but to fight and to
conquer, so little pains did they take to profit by their victories.
Hence, innumerable armies perished in Syria, without any other
advantage than that derived from the momentary success obtained by
superior numbers.
It was by the neglect of these principles, also, that Charles XII,
abandoning his line of operation and all communication with Sweden,
threw himself into the Ukraine, and lost the greater part of his army
by the fatigue of a winter campaign in a barren country destitute of
resources.
Defeated at Pultawa, he was obliged to seek refuge in Turkey, after
crossing the Nieper with the remains of his army, diminished to little
more than one thousand men.
Gustavus Adolphus was the first who brought back the art of war to its
true principles. His operations in Germany were bold, rapid, and well
executed. He made success at all times conducive to future security,
and established his line of operation so as to prevent the possibility
of any interruption in his communications with Sweden. His campaigns
form a new era in the art of war.