The first Ottoman army had been composed entirely of Turkmen nomads, who had remained largely under the command of the religious
orders that had converted most of them to Islam. Armed with bows and arrows and spears, these nomadic cavalrymen had lived
mostly on booty, although those assigned as ghazis to border areas or sent to conquer and raid Christian lands also had been
given more permanent revenues in the form of taxes levied on the lands they garrisoned. These revenue holdings were formalized
as mukвta'as, held by tribal leaders and ghazi commanders who used their revenues to feed, supply, and arm their
followers. It was this type of mukвta'a that developed into the Ottoman form of fief--called a timar--that was the
basis of Ottoman military and administrative organization as the European portions of the empire were conquered from the vassals
in the 15th century and placed under direct Ottoman administration. These nomadic troops had predominated through Orhan's
reign, until he saw that such undisciplined cavalrymen were of limited use in besieging and taking large cities. In addition,
once he had established his state, he had found it difficult to maintain order with such an army because the nomads still
preferred to maintain themselves by looting, in the lands of their commander as well as in those of the enemy.
To replace the nomads, Orhan organized a separate standing army of hired mercenaries paid by salary rather than booty
or by timar estates. Those mercenaries organized as infantry were called yayas; those organized as cavalry, mьsellems.
Although the new force included some Turkmens who were content to accept salaries in place of booty, most of its men were
Christian soldiers from the Balkans who were not required to convert to Islam as long as they obeyed their Ottoman commanders.
As Murad I conquered more and more of southeastern Europe, these forces became mainly Christian, and, as they came to dominate
the Ottoman army, the older Turkmen cavalry forces were maintained along the frontiers as irregular shock troops, called akncis,
who were compensated only by booty. As the yayas and mьsellems expanded in numbers, their salaries became too burdensome
for the Ottoman treasury, so in most cases the newly conquered lands were assigned to their commanders in the form of timars.
This new regular army developed the techniques of battle and siege that were used to achieve most of the 14th-century Ottoman
conquests, but, because it was commanded by members of the Turkish notable class, it became the major vehicle for their rise
to predominance over the sultans, whose direct military supporters were limited to the vassal contingents.
Only late in the 14th century did Murad I and Bayezid I attempt to build up their own personal power by building a military
slave force for the sultan under the name kapkulu. Murad based the new force on his right to a fifth of the war booty, which
he interpreted to include captives taken in battle. As these men entered his service, they were converted to Islam and trained
as Ottomans, gaining the knowledge and experience required for service in the government as well as the army, while remaining
in the sultan's personal service. During the late 14th century this force--particularly its infantry branch, the Janissary
corps--became the most important element of the Ottoman army. The provincial forces maintained and provided by the timar holders
constituted the Ottoman cavalry and were called spahis, while the irregular akncis and salaried yayas and mьsellems
were relegated to rear-line duties and lost their military and political importance. But, when Bayezid I abandoned the ghazi
tradition and moved into Anatolia, he lost the support of the Turkish notables and their spahis before his new kapkulu army
was fully established. He therefore had to rely only on the Christian vassal forces at the Battle of Ankara, and, although
they demonstrated considerable valour and fighting ability, they were overwhelmed by Timur's powerful army.
When the Ottoman Empire was restored under Sultan Mehmed I, the Turkish notables, in order to deprive the sultan of the
only military force he could use to resist their control, required him to abandon the kapkulu, justifying the action on the
basis of the Islamic tradition that Muslims could not be kept in slavery. The European and Anatolian revolts that arose early
in the reign of Murad II were at least partly stimulated and supported by members of the kapkulu, as well as the Christian
slaves and vassals who had been losing their power to the Turkish notables. As soon as Murad II came to power, however, he
resumed earlier efforts to make the sultanate more independent, building up the strength of the Janissaries and their associates
and playing them off against the notables. He distributed most of his conquests to members of the kapkulu force, occasionally
as timars but more often as tax farms (iltizams), so that the treasury could obtain the money it needed to maintain the Janissary
army entirely on a salaried basis. In addition, in order to man the new force, Murad developed the devsirme system of recruiting
the best Christian youths from southeastern Europe.
Whereas Mehmed II used the conquest of Constantinople to destroy the major Turkish notable families and build up the power
of the devsirme, Murad sought only to establish a balance of power and function between the two groups so that he could use
and control both for the benefit of the empire. Thus he enlarged the concept of kapkulu to include members of the Turkish
nobility and their Turkmen spahis as well as the products of the devsirme. Now only persons accepting the status of slaves
of the sultan could hold positions in the Ottoman government and army. Persons of Muslim and non-Muslim origin could achieve
this status as long as they accepted the limitations involved: absolute obedience to their master and the devotion of their
lives, properties, and families to his service. After this time all important ministers, military officers, judges, governors,
timar holders, tax farmers, Janissaries, spahis, and the like were made members of this class and attached to the will and
service of the sultan. The salaried Janissary corps remained the primary source of strength of the devsirme class, whereas
the spahis and the timar system remained the bases of power of the Turkish notables. Mehmed II thus avoided the fate of the
great Middle Eastern empires that had preceded that of the Ottomans, in which rule had been shared among members of the ruling
dynasty and with others and rapid disintegration had resulted. The Ottomans established the principle of indivisibility of
rule, with all members of the ruling class subjected to the absolute will of the sultan.