Wars are caused and created by a lot of things such as: a call to arms by their god, the taking of other country's property or territory, the need for certain material assets such as oil, racial, creed, or tribal hatred, the desire to enslaved defeated nations, and occasionally to satisfy the military desires of one's own armed forces. There are a lot of reasons for war, just as there are a lot of reasons for arguments, some justified, some not, but war is seldom a very good answer, and subsequently, war should not be called upon unless as a true necessity, and specifically in ordinary circumstances for the defense of the state.
In today's world, borders have never been more opened, as well as the fact that the largest corporations aren't domestic and thereby just transacting businesses within their own borders, but are truly international, in which there are many such international corporations, that actually make more profits and conduct more business outside of their own nation than they conduct within it. All of this makes sense, because the world is a very big place, even if your country is in aggregate one of the richest, it's aggregate riches are still significantly short of what the rest of the world has to offer up on their plate. In addition, seeking growth from countries outside your domestic borders is a proven way to increase both sales and profits.
The fact that trade borders have more and more been torn down or modified so as to reasonably accept and trade goods country to country, basically benefits all involved, for the basic reason that if a given country can produce a given product at a lower price point, even with the transportation and insurance costs taken into account, than those consumers of such products are benefiting, and monies that would have been spent at a higher price point, have been saved for either investment or other purchases. That said, domestic industries do matter, so that it is reasonable to have trade agreements that reflect that a reasonable accommodation must be made for domestic industry, which is reflected in tariffs, temporary or not, sliding scale or not, and in general trade agreements that try to smooth out import and export amounts between countries.
Those countries that fairly trade with one another, are consequently, far less inclined, to desire to go to war, because fair trading between nations, allows each to benefit in turn, and a rising boat of prosperity not only is beneficial to the people, but almost always results in less domestic unrest, as when the people are well sheltered, fed, and have decent healthcare, they are far less restless, than when there is nothing but the general lack of these things.
However, as in all things, there are a couple of important caveats, of which one, is that not every country engages in open trade, in addition to the fact, developing countries, may be unfairly and in actuality exploited for their natural resources or similar, by more developed nations, so that the greatest benefit of infrastructure and resource development within those nations, occurs not to the indigenous people, but to those that have structured business and trade deals that benefit them to an unfair degree, leading to legitimate resentment, especially so when the biggest beneficiaries in a target nation, are the elite of that country, with the people barely benefiting whatsoever.
In all, though, trade between nations is primarily good, especially so when that trading does not allow one nation to hoodwink another, such as when precious metals are exchanged for mere trinkets and mirrors, for as long as trade truly benefits each country, wars, will as a matter of course, simply fade away.