Naval power projection has always been a critical component of wars between states, particularly for nations with expansive coastlines or overseas territories. A powerful navy allows a country not only to defend its shores but also to project its might overseas, blockade enemy ports, secure vital sea routes, and provide logistical support to land campaigns. Historically, the British Empire's dominance was underpinned by its formidable Royal Navy, which played a crucial role in wars against France, Spain, and Germany. The Pacific theatre of World War II also highlighted the significance of naval power, with key battles like Midway determining control over vast oceanic expanses and influencing the broader trajectory of the war.

Anti-war movements, which gained considerable momentum, especially during the 20th century, have played a significant role in shaping public opinion and, by extension, policy decisions related to wars between states. The Vietnam War is a notable example, where widespread public protests against the conflict significantly influenced U.S. policy and expedited American withdrawal. Such movements, propelled by civilians' desire for peace, often highlight the human and economic costs of war, exerting pressure on governments through protests, media campaigns, and civil disobedience. The presence and impact of anti-war movements serve as a check on state decisions, demanding accountability and compelling leaders to justify their war efforts to the public.

The concept of 'total war' has been especially prevalent in the 20th century, wherein nations mobilise all their available resources, both civilian and military, towards the war effort. This means that not only are soldiers involved in combat, but the entire civilian population is also engaged, either directly in manufacturing and other supporting roles or indirectly by facing the ramifications of war. The World Wars epitomised this concept. Cities were bombed, economies were restructured for war production, and propaganda was used to rally the populace. The blurring of lines between combatants and non-combatants in 'total war' meant that wars between states had widespread and often devastating consequences for civilian populations.

International treaties often play a dual role when it comes to wars between states. On one hand, they can act as deterrents to conflict. Treaties like the Treaty of Tordesillas (1494) or the NATO alliance are intended to prevent conflicts by either demarcating territories or by pledging mutual defence. On the other hand, the violation of treaties or disagreements over their terms can lead to war. For instance, Germany's violation of the Treaty of Versailles' provisions was among the causes of World War II. In the aftermath of wars, treaties like the Treaty of Paris (1783) or the Treaty of Versailles (1919) delineate terms of peace, reparations, and territorial adjustments.

Economic motivations have historically been significant drivers behind wars between states. Nations often engage in conflict to secure valuable resources, such as oil fields, mineral-rich territories, or fertile lands. The quest for resources not only ensures a state's self-sufficiency but can also boost its economic prosperity. Furthermore, controlling trade routes, such as maritime chokepoints or land-based Silk Roads, provides a nation with considerable economic and strategic leverage, often leading to conflicts. The Scramble for Africa in the late 19th and early 20th centuries exemplifies this, where European powers raced to claim African territories, driven largely by the continent's vast natural resources and economic potential.