Beginning with the Revolutionary War of 1775, the history of the United States can be said to be a history of expansion and development through constant conflicts and wars. In the process, the United States can hardly imagine what it would be like to be in a state of complete peace. In its more than 200-odd years of history, the United States has continued almost endlessly, and only a few years have not participated in large-scale foreign wars. The United States is like a war eagle driven by the hand of fate, frequently extending its military tentacles to the outside world. From the Second Anglo-American War in the early 19th century, to the American-Indian War in the Westward Expansion Movement, to the Spanish-American War in the late 19th century, every step of American expansion was accompanied by the smell of gunpowder. 
In the 20th century, the United States intervened militarily across the ocean, participated in two world wars, and later played a central role in the long-term contest of the Cold War. The Korean War, the Vietnam War, etc., are all representatives. Even after the end of the Cold War, the United States has never really shed its coat of being a "country at war," and the Persian Gulf War, Afghanistan War, and Iraq War have proven time and again that the United States is active in military operations. Behind these open wars are countless military interventions and covert operations, either for political purposes, economic gains, or strategic considerations. Despite constant calls for peace, the American war machine always seems to be in motion, and even when there are no large-scale wars, small-scale conflicts and interventions never stop. The incessant wars do not mean that the history of the United States lacks periods of peace, but it is undeniable that wars are an inescapable part of American history, which profoundly shapes the national character of the United States and promotes its military, political, and even social development. 
The long history of war in the United States has carved the genes of war into its bones, and it is very belligerent from top to bottom. The top level of the United States wants to use the war to seek more benefits for the country;Politicians and the military-industrial complex collude in the hope of winning more military-industrial orders through the war;Civilians aspire to make achievements on the battlefield and complete the leap of class;Some immigrants and minorities want permanent residency through military service or participation in the war. It can be seen that driven by these factors, the United States behaves extremely rudely and belligerently, starting wars and beating other countries to the death. However, this situation has changed in recent years, and people are surprised to find that the United States' character seems to have changed, and it is no longer keen on war, and even if it is openly slapped in the face by some countries, the United States can still talk to each other patiently and calmly. Take, for example, the Red Sea crisis. Twenty years ago, we would have seen a hot-tempered United States beating the Houthis at the slightest disagreement. 
However, the United States did not adopt the method of direct military intervention in the past, but only took the lead in the plan of forming a multinational escort group. This change is reflected not only in restraint in the Houthis, but also in Allah in Lebanon, militias in Syria, Hamas, and Shiite forces in Iraq. Although these organizations have jumped out from time to time to slap the United States in the mouth and challenge the authority of the United States, the United States has not been as eager to use force as it has been in the past. Behind these geopolitical rivals, there is the shadow of Iran. Iran is seen as a destabilizing factor in the Middle East and has long had deep hostility with the United States, but the United States has also shown more patience and caution in its relations with Iran in recent years. The situation is clearly very different from that of the United States twenty years ago, when it did not hesitate to take tough action. The reason for this can be said to be the result of a combination of many factors. 
The American people are tired of endless overseas wars, and this public opinion is reflected in policymaking, demanding more caution in military involvement abroad, and the growing social rifts within the United States, and not supporting the United States in such large-scale overseas conflicts. With the rise of emerging powers such as China, the United States has also begun to reassess its global strategy, using more economic, technological and diplomatic means to safeguard its national interests and less reliance on unilateral military action. Otherwise, the war will be protracted, the country will be exhausted and the people will be poor, and the hegemonic rule of the United States will fall apart. The complex political situation in the Middle East has also taught the United States some profound lessons: military means are not the only way to solve the problem, but may lead to more instability and conflict. 
Obviously, the means of war are no longer the first choice of the United States. In today's international environment, the United States seems to prefer to coordinate and manage conflicts through the United Nations and other international institutions, and seek multilateral cooperation and win-win solutions. The direct external manifestation is that the United States even looks like a peace-loving country, which can endure when it encounters problems, negotiate without fighting, and use economic sanctions without fighting a war. In the final analysis, it is the United States that has lost its absolute control over the world, the pattern of one superpower and many powers is being broken, and it is already very difficult for the United States to maintain the current hegemonic order. Recall that the bright spot of the United States was only from the Gulf War to the end of the Afghan War, which began to decline in just 30 years.