How? Sacking cities, executing the leaders, enslaving the populance, killing those who oppose you... pretty standard for the time period.
That is how all empires work.
Well, yes. This has been my point more or less the whole time. Creating "empires" requires a certain measure of brutality.
Whether or not the Romans were any more or less brutal than the other "empires" of their era isn't really important. The fact remains that they relied entensively on the use brutal force in order to intimidate their opponents into submision and expand the limits of their political influence. Furthermore, they were largely successful in these efforts. Out of necessity, this is simply how wars of conquest generally tend to fought. There just really isn't any "good" way to "humanely" quash a people under the boot heels of your military.
Unlike what Sketchbook was suggesting, however; the Romans approached such brutality in a logical and essentially limited manner. Their violence was also tempered with a certain measure of security and social generosity.
While I guess that you might bring up the modern concept of winning "hearts and minds" as evidence of a less brutal methodology being used to pacificy nations, I would argue that it is brute force and the sheer political and military stamina of the combatants involved which ultimately tends to decide the outcomes of such issues regardless. The modern concept of "economic development vs brutal conquest" has something of a mixed track record (the NVA and Vietcong, for instance; were rather brutal in comparison to the US and the French and by-and-large did not have the suport of the Vietnamese people, but still managed to win the strategic war due to their geater staying power). Additionally, I think it should be noted that, outside of WW2, the Cold War antics of the Soviet Union, and a few other scattered instances across the globe, no one has really fought an honest "war of conquest" for at least half a century. The objective of most modern warfare seems to be centered more around getting in and getting out again quickly than ensuring any lasting military presence or cultural assimilation.
The reasons for this change have already been addressed thoroughly (the effectiveness of "Asymmetrical Warfare" in the modern era, the concept of "Human Rights" endorsed by the dominate Western powers, the proliferation of the mass media, the growth of the concept of "Nationalism," the relative size and effectiveness of modern militaries in comparison to the populations of modern nation states, etca, etca..) so I will not discuss them here. However, as I have already noted, this may not always be the case.
"Empires" need a certain measure of brutality in order to function, and to claim that we have seen the last of such political structures would strike me as being more than a little naive.
All strategies have weaknesses. The Mongols was their horses. Burn everything and leave nothing for them to eat and they will suffer the same fate as the Huns.
It is worth noting the fact that the Mongols had to repeatedly use their terror attacks (judging by the insane death tolls) imply they didn't work- they did not cause the enemy to surrender their major cities without a fight.
The Mogols were able to destroy many of the largest and most heavily fortified cities of their age using such tactics. However, you are correct. All strategies have their weaknesses.
The Mongol's cavalry dominated armies were next to worthless in densely forested areas or on extremely rought terrain (i.e. Vietnam, Central Europe). Their bows also tended to perform poorly in very damp environments. On the dry, open plains of the Eurasian steppes, the Middle East, and China, however; the Mongol's were well nigh unbeatable. They were ultimately only really undone by the chaotic nature of their own government and the limits of their supply lines.
That is because the strengthens the ruling government. However they are brutal- few nations on Earth are close to self-sufficient and the standard of living, not to mention military hardware, starts to degrade after an extended blockade. It does destroy the country- why do you think the loses were even more one-sided in the 2nd Gulf War than the 1st?
Embargos can be very successful from an economic or military standpoint. They simply have a VERY mixed record when it comes to actually accomplishing regime changes or forcing nations to conform with international rulings. In fact, they often seem to only strengthen the resolve of the peoples' they deprive of essential goods. Castro's Cuban regime, for instance; has successfully resisted a rather thorough US embargo for well over half a century.
To bad they were importing Poles as slave labor into the Reich.
They did the same with the Jews. I think we all know what the Nazis ultimately viewed their "end game" as being where these people were concerned.
What did the Mongols give?
The "privilege" of not being butchered like livestock.
In all seriousness, however; association with the Mongols also ensured a certain degree of military security and trade with newly conquered lands.
Life is cheap. A UAV is millions of taxpayer dollars. They just have to outlast our willingness to spend money to win and all these new toys are extremely expensive.
True, but you must admit that "asymmetrical" wars are becoming easier and easier to fight with each passing decade.
Just compare the death tolls of the wars in Iraq or Afghanistan with those of the Vietnam War or the Soviet occupation of Afghanistan to see what I mean. We have been able to achieve some truly insane "kill to casualty" ratios through the use of modern technology. Things still might not exactly be a cake walk, but professional militaries can certainly be said to be bridging the tactical advantage gap that "asymmetrical" forces have traditionally held over them.
So it only works when you are already in a position of strength and dominance...
Not necessarily, insurgent movements across the globe have been able to rather effectively utilize "brutal warfare" tactics in order to draw media attention to themselves and discredit the professional militaries opposing them.
Additionally, the Vikings were able to use extremely "brutal" tactics in order to intimidate much of Western Europe into compliance with their demands in spite of technically being much less developed in terms of population, industry, and overall military strength than most mainland European kingdoms.
It all depends on what you are trying to accomplish.