The Islamic conquests are one.
In the name of Allah, the most Beneficent, the
Most Merciful
by the night as it enshrouds
by the day as it illuminates
by Him Who created the male and female
indeed your affairs lead to various ends.
For who gives (of himself) and acts righteously,
and conforms to goodness,
We will give him ease.
But as for him who is *****rdly cleaning himself,
self-sufficient and rejects goodness,
We will indeed ease his path to adversity.
Nor shall his wealth save him as he perishes
for Guidance is from Us
and to Us belongs the Last and First (92:1-14)
Muhammad was able to win the early support of some of his relatives and
close friends. His first converts were his wife, his cousin Ali, and Abu Bakr,
a leading merchant of the Koraysh tribe who was highly respected for his
integrity. Abu Bakr remained the constant companion of the Prophet during his
persecution and exile and later became the first caliph (leader) of Islam. But
opposition to Muhammad's message was very strong, especially from Mecca's
leading citizens. Many thought Muhammad was a poor poet attempting to pass on
his own literary creations as the word of God. Others believed him to be
possessed by demons. Muhammad's strong monotheism worried those residents of
Mecca who obtained their income from the pilgrims to the Kaaba. Most of
Muhammad's early converts were among the poorest of the city's residents, and
Mecca's leading citizens feared social revolution.
http://history-world.org/islam2.htm
Many had assumed that Islam was simply the militant imposition of the culture of 7th century Arabia on illiterate Third World tribes, with little relevance to the developed nations of today. However, the events of September 11, 2001, certainly have punctured the comfort of those nave presumptions. Islam has been, from its inception, a militant warrior code with an agenda of world conquest. Now, with its possession of nuclear weapons, its agenda can no longer be ignored.
Mohammed was born at Mecca, Arabia, in a.d. 570, and his Islam quickly spread beyond the borders of the tribal groups of Arabia. The 7th century was startled with the rapid advances of his militant religion: Syria fell in 634; Jerusalem in 637; Egypt in 638; Persia in 640; North Africa in 689; and Spain in 711. Both Christians and Jews throughout Europe were terrified until the Islamic troops were halted by Charles Martel at the Battle of Tours, France, in 732.
http://www.khouse.org/articles/2002/421/
The Muslim conquests brought about the collapse of the Sassanid Empire and a great territorial loss for the Byzantine Empire. The reasons for the Muslim success are hard to reconstruct in hindsight, primarily because only fragmentary sources from the period have survived. Most historians agree that the Sassanid Persian and Byzantine Roman empires were militarily and economically exhausted from decades of fighting one another. The rapid fall of Visigothic Spain remains a bit mysterious however.
Jews and Christians in Persia and Jews and Monophysites in Syria were dissatisfied and sometimes even welcomed the Muslim forces, largely because of religious conflict in both empires.[2] In the case of Byzantine Egypt, Palestine and Syria, these lands had only a few years before been reacquired from the Persians, and had not been ruled by the Byzantines for over 25 years.
http://en.wikipedia.org/wiki/Muslim_conquests
Also, WWII was caused by Hitler. He attempted a Coup de Tas twice, the first time he failed, the second time he succeeded. He then took control over Germany and created a tyranny. He wanted power so he expanded. He used Germany's loss during WWI to create anger in the Germans, so that they would support him.