Thessalonian

Tsimiskis (in Greek), was not nicknamed as Βουλγαροκτόνος = Boulgaroktonos. He didn't subjugate all of Bulgaria either.
What about Manzikert? It's irrelevant.

Kirialax

Tzimiskes (in Byzantine Greek) was not nicknamed "the Bulgar-slayer", but neither was Basil until the Angelid period.

Basil attempts to protect the freeholding soldiers against the large landowners worked, but it completely broke the capacity of the thematic system. The flexible and defence-oriented system that kept the Arabs out was not present to stop the Turks.

falcon

True about Tsimiskes; but he was emperor only for 7 years while Basil II for 49.

Manzikert? That battle that was won by treachery?

or Myriokefalon? where the Byzantines beat the Seljuks in the same place the following year?

Kirialax

The question is not the outcome of the battle, but the flexible nature or lack thereof of the now-broken thematic system. Even though the grade of the average thematic soldier during the early Arab invasions was quite low, the fact was that they held every hilltop and harrassed the Arabs constantly. Given that most of the Arab campaigns were simply major raids, they could not besiege every little akropolis fortress, making permanent gains west of the Tauros extremely difficult. When the Seljuk Turks arrived, this system did not exist anymore. Those soldiers had not been called up for the better part of a century, and Basil's centralization of power on Constantinople ensured that the now-powerless local aristocracies had no reason to stay and try to hold the fortresses. They simply returned to Constantinople.

Myriokephalon took place over a century later in a vastly different context.

falcon

I just brought it up as a reference in relation to Manzikert, because a lot of people think that these two battles destroyed the Byzantines.

Picard

From what I know, thematic system and military were based on those freeholdnig soldiers, and only Angeloi' and Comneni' neglect of theme system which caused feudalization of the Empire broke Byzantine defences.

Kirialax

The thematic system was in utter shambles when Alexios took the throne. He seems to have brought an end to the entire system through his land legislation. I'm not too familiar with the exact legal status of the soldiers during the Komnenian period, nor am I familiar with all of the recent scholarship. The older assumption was that the pronioa, a sort of feudal land grant took over as the main means of providing troops for the government. As I understand it, it is now believed that the pronoia existed much longer than previous believed, but was not as pervasive. I am not aware of any detailed study of army recruitment under the Komnenoi - Paul Magdalino touches on it in his book on Manuel and one of his articles, and I haven't read Bartusis' arguments on the late Byzantine army in any depth. I have not yet read all of Birkenmeier's book, so I can't comment on that, either.

Mosquito

For me Iustinian, for ordering Trebonianus making Corpus Iuris Civilis

Katophract

I've always been interested in Irene of Athens, Empress from797 to 802. Not the greatest, but that's not what the OP asked. I find her life and rule very interesting. Ended Iconoclasm and I'm thankful for that. (I'm too much of an artist to worry about the debate of idolatry.) I still wonder what would have happened if she had gone through the plans of marrying her son to the daughter of Charlemagne.

Yaunâ

Taxation and custom duties were some of the major revenues of the Empire. The gradual rise of the power of the Venetian, Genoese, and other merchants was catastrophic, but the results were shown after the Komnenian period mostly, although the process started during it (not only in Constantinople but various parts of the Empire). Not only they were free from taxes, but they managed to control the Byzantine seas later, including the Black sea at last, instead of the Byzantines.