Byzantine Empire under the Angeloi ended in 1204.
Yes, the Middle East attacked the Byzantine Empire, i.e. in the Levant. The Turks also attacked the Byzantine Empire.
The Russian people attacked the Byzantine Empire
Constantinople was the capital of the Roman/Byzantine Empire 330 to 1204 and 1261 to 1453
Timothy Dawson has written: 'Byzantine cavalryman, c.900-1204' -- subject(s): Military History, Byzantine Empire, Byzantine Empire. Stratos. Cavalry
The empire was overtaken by the Catholic Crusaders in 1204 AD, but it was taken back in 1261 AD. It was weakened, but it did not disappear.
Francois Bredenkamp has written: 'The Byzantine Empire of Thessaloniki, 1224-1242' -- subject(s): Latin Empire, 1204-1261, History
The KIevan Rus' attacked Constantinople and the Bosphorus.
Yes they did. They managed to conquer Constantinople in 1204 and formed The Latin Empire of Constantinople until 1261 when The Emperor of Nicea reconquered the City for The Byzantine Empire.
The crusades, originally intended to save the Byzantine Empire, among other things, failed to do this and hastened its decline instead. The crusaders sacked Byzantine cities and eventually captured Constantinople in 1204. They then used Constantinople as the capital of what is called the Latin Empire, which it remained, until the Byzantines managed to recapture it in 1264. The Byzantine Empire never really recovered from this, though it held on for almost another 200 years.
The collapse of the Western Roman Empire opened the Byzantine Empire to being attacked as well. The resources and troops were used for that, rather than being used to defeat the Persians.
The city of Constantinople, the capital of the Byzantine Empire, was sacked and partially destroyed by the armies of the Fourth Crusade in 1204. This attack on fellow Christians caused a centuries-long schism in the church and allowed the Turks to conquer parts of the Byzantine Empire.