The oldest approach to preserving peace is through diplomatic contact, with envoys sent from one head of state to another. A good diplomat knows all of the foregoing power factors and the interests of the countries involved and has some suggestions for reaching a compromise that leaves both parties at least partly satisfied. This is crucial:there must be a willingness to compromise. This is often very difficult, however, because countries define their vital, nonnegotiable interests grandly and are unwilling to cut them down to compromisable size. If successful, diplomats draw up treaties-contracts between countries-which must be ratified and, one hopes, observed. If one country feels a treaty harms it there is nothing to stop it from violating the bargain. Countries enter into and observe treaties because it suits them. Some observers say the United States and Soviet Union, both relative newcomers to the world of great-power politics, were unskilled at diplomacy, too unwilling to compromise. The climate of mistrust between them was one of the hallmarks of the Cold War.