In destructive economic systems, there is a feedback loop wherein it becomes self-confirming that greed and aggression lead to gains rather than acts that involve "playing by the rules", sharing profits, cooperating and helping others to prosper. As activities on Wall Street and in transnational corporations confirm, successful players are expected to produce income by any means possible, pay workers as little as required, charge as much as can be obtained for products and always tap into new markets for an enlarged customer base. It, also, requires a perception to be created that some newly devised product is desirable and must replace the older versions for which there is often built-in obsolescence.
In any case, new markets must always be found in order to raise financial yields. Any corporate manager who did not strive to develop them would quickly find himself in an unemployment office in addition to his being blacklisted by former colleagues.
This entire process, therefore, requires government leaders in support of their countries' industries to wrestle control of needed goods. Simultaneously, they have to convince the public that there are solid reasons to carry out assaults in resource rich regions of the world -- places like the Caspian Sea, with its oil estimates ranging up to about 200 billion barrels or 15% of total world reserves. Add to this treasure the fact that the Caspian Sea, also, is believed to contain 4% of the world's proven reserves of gas according to the Congressional Research Service, an organization supplying bipartisan information to Congress, in its report titled "Caspian Oil and Gas: Production and Prospects".
Indeed, its author Bernard A. Gelb, a specialist in industry economics, states: "There is a likelihood of relatively large reserves of crude oil and natural gas in the Caspian Sea region, and a consequent large increase in oil and natural gas production from that area. Because diversity of energy sources and energy security are considerations in Congressional deliberations on energy policy, this prospect could play a role in such discussions. However, there are obstacles to increases in Caspian Sea region production of oil and gas [such as Russia's and Iran's unwillingness to hand Caspian Sea resources over to U.S. control] that may slow development." He goes on to add: "However, Iran now can compete somewhat with the BTC pipeline through oil "swaps" that ultimately divert Caspian region oil away from Western, including U.S.,
markets. Iran has enlarged its tanker terminal at Neka on the Caspian Sea coast, enhancing its capacity to deliver Caspian oil to refineries for local consumption, with an equivalent amount of Iranian oil exported through Persian Gulf terminals." 
Put alternately, uncooperative countries, such as Iran and Venezuela, with assets coveted by western corporations give the perfect excuse to western governments to demonize them, threaten them and seek out destabilization of their regimes. All the same, the maligned nations will not let their reserves be plundered whether bullied or not by outside groups willing to use any means possible to obtain their prizes.
At the same time, it becomes quickly clear about whose interests they, ultimately, serve (rather than the public's) when government officials' desire for these contributions, lucrative future jobs after exiting public service and maximization of personal profits from their financial holdings are added into the mix. Indeed, "members of Congress invested nearly 196 million dollars of their own money in business that receive hundreds of millions of dollars a day from Pentagon".  So taken all together, these conditions provide plenty of motivation to keep the nation's war drums beating.
Therefore, wars are big business, most notably for investors and employees in the aerospace and defense industries. The related purposes, like the ones guiding most corporations, are hardly humanistic. Instead new sources of revenue, cheap resources from conquered lands, and new markets for products and services are the sine qua non.
Accordingly, the Pentagon and the corporations that supply goods and manpower for wars have one general intention in mind and that is not even to win wars. Winning wars would mean that money-spinning contracts and growth of the organizations' national and global influence would shrink. Jobs, then, would disappear, high salaries would not be commanded and gargantuan earnings would cut back if wars were, actually, won and, thus, completed.
Instead, the intention is to strengthen control of regions and their resources, open up new markets for one's own country's products, continually advance into new territories to create the same outcome and, eventually, dictate assorted policies across the entire world. Consequently, the U.S.A., despite having a $12T federal deficit, aims to advance its ongoing plans to have full-spectrum dominance over the economies, territories, politics, military affairs and other entire governments on a full global scale and in support of American enterprises.
It, also, means that an all-out attempt to quell the Taliban will take place since Afghanistan and Pakistan are both needed to move the fossil fuels to emerging markets and ensure that central Asian economies are tied to U.S. corporate interests rather than those of Russia and China. On account, it is critical that both latter nations be blocked if western dominion over Asian markets for obtainment of raw resources and sales of final products, i.e., fossil fuels, are to result.
In the same vein, American citizens are not much of a consideration. After all, markets and remuneration for oil and other supplies might be superlative in India, China or other lands with advancing economies and plenty of money to spare. As such, concern over protection of us from terrorists (the latest justification for carrying out assaults abroad in lands like Yemen) and any desire to improve the lives of peoples in the U.S. or developing countries are minor considerations at best. Instead, it is far more on the mark to ask, as did Woodrow Wilson: "Is there any man, is there any woman, let me say any child here that does not know that the seed of war in the modern world is industrial and commercial rivalry?"
As such, it is useful to bear in mind that warfare almost exclusively concerns resources and trade except for religious rivalries and the small scale fighting of feudal lords. With the desire to gain ever greater advantages for oneself and one's own group by taking these away from other subjugated groups, campaigns have always been perpetuated under false pretexts, especially so when energy supplies are involved.
It follows, then, that any politician not exhibiting Woodrow Wilson's stark honesty on this point is both a liar and a propagandist with the ulterior motive to control public perception so there is advancement of war. This understanding, if nothing else, should be absolutely clear.