When it comes to military expenditures, the United States spends the most per year by a large amount. In fact, they spend more than the next 8 countries spend combined. Despite the massive amount of military spending, the US appears much more reasonable when comparing military expenditures as a share of GDP.
The United States by far has the highest GDP in the world at nearly $20 trillion. China has been gaining ground in recent years, though is still a ways off at ~$14T. After that there is a precipitous drop off to the next biggest economies of Japan and Germany (~$4-5T).
With the worlds largest economy, the US military has played a role as global “peace keeper” since the end of WWII. There has certainly been conflicts (and many instigated and/or led by the US) but none on a large scale. The relative peace partly related to the US global military presence has allowed global trade to flourish and nations’ economies become more intertwined.
Timeline of Military Expenditures as Share of GDP
Though the US spends the most on their military, when expenditures as a share of GDP are factored in, Saudi Arabia has the highest percentage in the world. The Saudis spend a whopping 8-12% of their GDP on their military. With their oil based economy making them one of the wealthiest countries, Saudi Arabia has the means to afford all that spending on defense.
The worlds second largest economy, China, only spends ~2% of the GDP on their military. As their economic growth has skyrocketed, their military spending has similarly increased as well.
Despite the 28 nations of NATO signing an agreement in 2014 to bring their military spending as a share of GDP to 2%, only 6 countries have accomplished that so far. A major reason for the lower figure is due to Germany, the EU’s largest economy, only having a ratio of 1.2%. With US military bases scattered throughout Europe providing protection, there has been no urgency to increase military spending.
Source: Our World in Data