The chief achievements of both Leo and Constantine were their books. Those of Leo consist of a manual on the Art of War, some theological treatises, and a book of prophecies, a collection of political enigmas, which were long the puzzle and admiration of the East.(26) The first-named work is most valuable and interesting, bringing down the history of military organization, tactics, and strategy to Leo’s own time, and giving us a perfect picture of the Byzantine army and its tactics, as well as incidental sketches of all the enemies with which it had to contend. The backbone of the force was still the “themes” or “turmæ” of heavy cavalry, of which every province had one. The number of the provinces had been much increased since the days of the emperors of the house of Heraclius, and this implied a corresponding increase in the troops. They were raised from subjects of the empire and officered by the Byzantine nobility, for as Leo observed, “There was no difficulty in obtaining officers of good birth and private means, whose origin made them respected by the soldiery, while their money enabled them to win the good graces of their men by many gifts of small creature comforts, over and above their pay.” The names of some of the great noble houses are found for generation after generation in the imperial muster rolls, such as those of Ducas, Phocas, Comnenus, Bryennius, Kerkuas, Diogenes, and many more. The pages of Leo’s work breathe an entire confidence in the power of the army to deal with any foe; against Saracen, Turk, Hungarian, and Slav, instant and decisive action is advised; when caught, they should be fought and beaten. It is only when dealing with the men of the West, the Franks and Lombards, that Leo recommends caution and deprecates any rash engagement in a general action, preferring to wear the enemy down by cutting off his supplies and harassing his marches. We gather a very favourable impression of the Byzantine army from Leo’s book; it was organized, armed, and supplied in a manner that has no parallel till modern times. Each regiment possessed its special uniform, and was equipped with regularity. There was none of that variety in arms and organizations which was the bane of mediæval armies. The regiments had each attached to them an elaborate military train, a small body of engineers, and a provision of surgeons and ambulances. To encourage the saving of wounded men, Leo tells us that the bearer company was given a gold piece for every disabled soldier whom it brought off the field after a lost battle. It would be hard to find any similar care shown for the wounded till the days of our own century.