In general, expansionism consists of expansionist policies of governments and states. While some have linked the term to promoting economic growth (in contrast to no growth / sustainable policies), more commonly expansionism refers to the doctrine of a state expanding its territorial base (or economic influence) usually, though not necessarily, by means of military aggression. Compare empire-building, colonialism, and Lebensraum.

Irredentism, revanchism, "reunification" or pan-nationalism are sometimes used to justify and legitimize expansionism, but only when the explicit goal is to reconquer territories that have been lost, or to take over ancestral lands. A simple territorial dispute, such as a border dispute, is not usually referred to as expansionism.

Geographic enlargement of the United States has been classed as expansionism; but geographic enlargement of the European Union has not, perhaps because the EU is viewed as an organization rather than a nation, despite the centralization of some governmental functions in the organs of the EU.

Andrew J. Bacevich, Sr. (born 1947 in Normal, Illinois) is a professor of international relations at Boston University and a retired career officer in the United States Army. He is a former director of Boston University's Center for International Relations (from 1998 to 2005), and author of several books, including American Empire: The Realities and Consequences of US Diplomacy (2002), The New American Militarism: How Americans are Seduced by War (2005) and The Limits of Power: The End of American Exceptionalism (2008). He has been "a persistent, vocal critic of the US occupation of Iraq, calling the conflict a catastrophic failure." In March 2007, he described George W. Bush's endorsement of such "preventive wars" as "immoral, illicit, and imprudent." His son, also an Army officer, died fighting in the Iraq War in May 2007.

Bacevich graduated from the United States Military Academy at West Point in 1969 and served in the United States Army during the Vietnam War, serving in Vietnam from the summer of 1970 to the summer of 1971. Later he held posts in Germany, including the 11th Armored Cavalry Regiment, the United States, and the Persian Gulf up to his retirement from the service with the rank of Colonel in the early 1990s. He holds a Ph.D. in American Diplomatic History from Princeton University, and taught at West Point and Johns Hopkins University prior to joining the faculty at Boston University in 1998.

Jeff Halper (born 1946) is an anthropologist, author, lecturer, political activist, and co-founder and Coordinator of the Israeli Committee Against House Demolitions (ICAHD). In 1997, Halper co-founded ICAHD to challenge and resist the Israeli policy of demolishing Palestinian homes in the Occupied Territories, and to organize Israelis, Palestinians and international volunteers to jointly rebuild demolished Palestinian homes. He has created a new mode of Israeli peace activity based on nonviolent direct action and civil disobedience in the Occupied Territories. Halper was nominated for the Nobel Peace Prize by the American Friends Service Committee for his work "to liberate both the Palestinian and the Israeli people from the yoke of structural violence" and "to build equality between their people by recognizing and celebrating their common humanity".

Halper has written several books on the Israeli-Palestinian conflict and is a frequent writer and speaker about Israeli politics, focusing mainly on nonviolent strategies to solve the Israeli-Palestinian conflict.

Joseph Benedict "Joe" Hockey (born 2 August 1965), is an Australian politician and member of the Australian House of Representatives, representing the Division of North Sydney for the Liberal Party of Australia since 1996.

Hockey was a Minister in the Howard Government and is currently the Shadow Treasurer under Opposition Leader Tony Abbott in the Liberal/National Coalition.

Hockey was born in North Sydney as the youngest of four children. His father, Richard Hockey was born in Bethlehem (then in the British Mandate of Palestine) and migrated to Australia in 1948. Hockey is of Armenian and Palestinian background and the family name was originally Hokeidonian. Hockey attended St Aloysius' College in Milson's Point and the University of Sydney, residing at St John's College, where he graduated with degrees in Arts and Law. While at university he was President of the Student Representative Council. He was a banking and finance lawyer, and Director of Policy to the Premier of New South Wales, before entering politics.