I've changed the category of this question. Wikipedia has done an excellent job of listing all empires and the size of the landmass that was under their control. As explained in the related link, Wikipedia states: "The calculation of the land area of a particular empire is controversial." However, the two empires, the British Empire and the Mongol Empire, really stand out at the top of the list. The Russian Empire also in terms of landmasses comes to the top of the list. Generally, to build these empires took many generations of extremely aggressive regimes, so I can not specify a single leader who conquered the most land. However, in the great conquests for land, Genghis and his son, Ogedei Khan stand out in the history of empires. In terms of landmass of these empires, as indicated by Wikipedia, the top empires, had control over 20- 30 million square km. Wikipedia states the landmass of our planet is 148 million square km, so the greatest empires extended their control over ~ 20% of the planet. The more recent wars, (WW I and II), are around ~3 million square km, around 2% of the planet's land mass.
The Romans took over a lot of places, but most of the places were ruled by Germanic tribes, whom the Romans considered "barbarians"
The Balkans
The group with took over most of Europe after the fall of the western part of the Roman Empire eventually were the Franks. They did not do so immediately. They took over gradually.
The one who took no prisoners
Gerald Ford took over office without being elected. Hope you liked? Ciao~
In 1936-37: none. (In 1936 they remilitarized the Rhineland, but as the area had remained German there was no take over). The first area that the Nazis took over was Austria in 1938.
They took over Wales and what later came to be called England, but not Scotland.
When the English took over New York where did resedints live
Took over so much area the armys also joined as a big one
San Juan Capistrano ended in service in 1864, due to the fact that the Native American Indian took over the inside and they took it over for ever.
After the Mogul Empire fell Great Britan took over most of India.
Agribusinesses took ownership of most of the land.