Final answer:
The concept in question refers to collective security, which was the founding principle of the League of Nations created after World War I to maintain world peace and ensure mutual protection for its members.
Step-by-step explanation:
The concept of bringing all nations together to ensure territorial integrity and independence is best characterized by the establishment of the League of Nations. This organization was formed after World War I as part of the Treaty of Versailles. The League's primary objective was to maintain world peace by promoting collective security. An attack on one member country was intended to be considered as an attack on all, thereby guaranteeing political independence and territorial integrity for both large and small nations equally.
President Wilson strongly advocated for this international organization in his Fourteen Points speech, which outlined his vision for a postwar world. His efforts led to the creation of the League of Nations as a forum where nations could work together to avert another world war, protect human rights, and enforce justice and treaties. Nationalism, on the other hand, emphasizes the importance of asserting a nation's interests above those of others and promoting self-rule for people with common backgrounds. However, the League of Nations was about collective security and international cooperation beyond nationalism.
In summary, collective security is the principle that underpins the notion of all nations allying to preserve each other's territorial and political sovereignty, which is exemplified by the League of Nations.