COLONIALISM
Colonialism is the expansion of one nation over other territories and peoples, in order to dominate their resources and trade. So also it is called the set of reasons used to legitimize the system. The Colonialism is possible in general when the values of the colonizers are superior to those of the colonized, and in particular the technology and the economic gap are so great that the colonized aren't able to oppose and stop the colonization.
Strictly speaking, it is called 'colonialism' the dominance maintained by different European countries on other territories outside Europe, starting from the end of 1400, simultaneously with the geographical explorations, and formally concluded after the Second World War with the victory of USA and USSR.
In practice, the victory of these powers and their prevalence on the world stage has given way to a relatively new type of colonialism, namely the political, based on terror of atomic apocalypse, on the superiority of the military means and the will to use them to advantage and in the interest of the stronger.
The Monroe Doctrine at the beginning of 1800 sanctioned the USA's superiority and essentially declared their right to meddle in the affairs of Latin American states, to drive out and take the place of the Europeans 
The need to give space to white settlers led Instead inside the USA to the ruthless oppression and extermination of native primitive peoples. What today would be considered an illegal land occupation and genocide, for white Americans of the time was considered a right.
Similarly the USSR, in order to establish communist systems dependent on Moscow, and occupying the space vacated by the former colonizers, they sent military mercenary forces (Cubans of Fidel Castro) in African countries Angola and Mozambique and in many others, to destabilize their political systems and drive out the last Europeans who had established many business, thriving almost everywhere.
Unfortunately, the consequences of this policy are plain for all, because a few African countries have managed to improve the level of safety and life prior than decolonization. Most, especially those administered by so said 'socialists' governments, instead are reduced to abject poverty, despite their enormous natural wealth.
As for Russia, even before the USSR's birth, the Tsarist colonialism had seized some western states such as Ukraine and the Muslim and Asian states, that is, those Soviet republics that, after the USSR's fall, in part would become independent states.

AN EXAMPLE OF SUCCESSFUL COLONIALISM THAT HAS ORIGINATED THE WESTERN CIVILIZATION: leaving aside certain historical stupid and unmotivated legends, mostly due to ignorance or ideology, or even racism or parochialist foolishness, it is undeniable that the ancient Romans created their empire to objective needs, not only with the force of weapons, but with their way of live and their multi-ethnic and multicultural approach, which resulted in the adhesion and collaboration of almost all peoples.
The people becoming part of the Empire, recognizing the superiority of the way of life, the organizational technological capacity and also of Romans' ethics and law, were integrated and worked together to consolidate themselves.
For already more than a century, and more before the fall, the imperial armies were mostly composed of non-Roman legionnaires and Germanic barbarians, and the emperors were no longer always Italic. But even if there had been periods of strife and anarchy, the empire continued to remain standing, despite the ambitions and infighting..
The Roman Empire in the West fell under the pressure of invaders coming from the Asian steppes and pressing on the Germanic peoples, and in addition to internal struggles for the incapacity and corruption of the central government, but mainly by the corruption of morals, the denatality and since when the Emperors had abandoned Rome.. But without the Roman Empire in Europe, the world, and our culture without doubt wouldn't be those that we know today.
European languages: even those idiom who aren't neo-Latin, take directly or indirectly from Latin, including memory and insignia of the imperial glories. For example the word KAISER, like CZAR are from the deformation of the Latin CAESAR, the Roman Pontiff is called so because in the Roman Empire was the post of Pontifex, the calendar itself is Latin, including the names of months and almost all the days of the week.
All the European legal systems are based on the principles of Roman law, in some eastern states the Church follows even the Julian calendar not reformed by Pope Gregory.
All peoples, even the invaders, acknowledged the superiority of the system, much that decided to perpetuate it (see the 'Holy Roman-Germanic Empire' which arose after the failure of the attempt to establish a Lombard kingdom in Italy). The existence of the Empire and its road infrastructure and civil security has also made possible the rapid spread of Greek and Roman civilization and the Christianity in the Roman world and beyond.

Lino Bertuzzi - Rome, Jan, 2014