First, it's important to note the implied marriage between foreign policy and national security. Foreign policy is designed to promote national interests abroad and national security is designed to protect a nation from foreign threats.

There has been a tremendous transformation within the U.S. since its inception in the way it approaches national security. Leaders, geography, popular sentiment, and technology have all played pivotal roles in shaping the nation's ever-evolving security policies.

Shortly after the U.S. gained independence in 1783, the greatest security threat to the fledgling nation was posed by rival European powers.

Consequently, a trade dilemma between a warring France and Britain during the French Revolution from 1789-1799 inspired the

Jay Treaty, initiating a period of American neutrality regarding European conflicts and peace through trade.

It wasn’t until Thomas Jefferson’s presidency that the U.S. was re-envisioned as an “Empire of Liberty," which furthered its land expansion and worked to solidify the U.S. as a pinnacle for democracy for the rest of the globe.

The post-Jefferson 19th Century was largely focused on land acquisition, limiting European influence in the region, and eliminating any domestic threats such as the native populations.

The Monroe Doctrine (1823) set the precedent for a longstanding U.S. policy of regional control over the New World in hopes of creating stability, security, and trade in the Americas.

Divisions over state and federal authority hindered widespread U.S. nationalism. However, manifest destiny played a major role intertwining broad U.S. nationalism while also supporting expansionist policies.

The Louisiana Purchase (1803), the Monroe Doctrine (1823), the Trail of Tears (1830), the Annexation of Mexico (1848), the acquisition of Oregon (1848), and the Roosevelt Corollary (1904) were all inspired, or justified, by this divine ideology.

Land expansion and the structuralized destruction of native populations were justified as a means to increase the size and resources of a developing nation while eradicating domestic security threats.

U.S. imperialist policies strengthened with rising industrialization and the emergence of the U.S. Navy toward the late 19th Century. The acquisition of Cuba, Puerto Rico, the Philippines, and Guam as a result of the Spanish-American War (1898) solidified the role of the U.S. as a major world power.

Throughout the 19^th Century the U.S. (with minimal moral or legal obligations) established a viable industrialized nation, with a powerful army and navy, sound borders to protect from possible foreign invasions, and de-facto colonies to exploit their natural resources.

Woodrow Wilson popularized a

lasting ideology labeled “Wilsonianism,” or “American Exceptionalism,” which idealizes the U.S. as a “city upon a hill.” According to this perspective, the U.S. is unique and exceptional in regards to democracy, individualism, egalitarianism, laissez-faire, and republicanism.

Throughout WWI, the U.S. sold weapons to reap the economic benefits of war while hoping to remain neutral (due to popular sentiment and leadership). But eventually the U.S. was dragged into the war.

Shortly after, the U.S. passed the Espionage Act of 1917 -- a document that has been frequently amended and has recently resurfaced as the primary means to accuse whistle-blowers like Edward Snowden and Bradley Manning with “aiding the enemy.”

WWII is largely credited for creating the modern political world structure.

The U.S. initially didn't want to get involved. However, Pearl Harbor and the economic incentives to industrialize while still recovering from the Great Depression provided popular support for the war.

After the war, the U.S. and USSR emerged as the top two global superpowers.

Heavy industrialization, along with the lack of damage to American infrastructure during the war (as seen throughout Europe), was pivotal for the U.S. to emerge as the dominant western power.

However, the fall of Nazi Germany was followed by the rise of the communist Soviet Union. Containing communism became the official national security policy of the U.S. after WWII, but efforts to contain the Soviets started during the war.

Hoping to thwart the USSR and the spread of communism by gaining favor with nations recovering from the effects of WWII, the U.S. instituted the Marshall Plan (1948), and later the Eisenhower Doctrine (1957).

Funding and economic relief were primary means to combating the spread of communism, especially while establishing friendly relations with the nation's bordering states. However, the conventional and nuclear arms race was the ever-present security concern.

Mutual Assured Destruction (the idea that the U.S. and USSR engaging in nuclear war would be the death of everyone) was the nation's official and only national security policy which was designed to effectively thwart nuclear war.

This intensified the extremely profitable global arms trade to an entire new level as the Soviets and the U.S. now manufactured weapons to sell to nations for U.S.-Soviet based proxy wars (as seen in Korea, Vietnam, and Iran-Iraq).

Concerns over regional stability inspired a long standing history of overthrowing democratically-elected governments throughout Latin American and/or implementing or supporting an oppressive dictator in the name of combating communism.

The 1960s through early 90s marked a period of economic and political suppression of rising Latin American leftist movements (as seen in Cuba, Chile, and Nicaragua).

In terms of national security, the Cold War initiated a global arms race which called for increased intelligence gathering, spying, and international alliances. This solidified the roles of the CIA, NSA, NATO, and the U.N. in national security.

The technological progression since the early 1990s regarding computers and the Internet -- combined with the September 11 attacks -- has birthed new controversial security policies which walk the line between national security and national defense.

The “Bush Doctrine” (known for the PATRIOT Act and endorsing the War on Terror) authorized a new era of spying and preventative war. President George W. Bush left a legacy of cyber-warfare, security trumping privacy, extra-judicial killings (e.g. drone strikes), and privatizing military forces.

The U.S. continues Bush’s legacy of pursuing “imminent threats” with drones, unlawfully detaining uncharged suspects at Guantanamo Bay, and privatized security forces which essentially operate as U.S. mercenaries.

However, cyber security and drone warfare appear to have the most promising -- while controversial -- future for U.S. national security.

Drones provide the U.S. with the means to conduct military operations without the political repercussions of endangering the lives of its troops. However, they are also known for killing civilians which the government labels “collateral damage.”

The future for drones becomes even more controversial as the Defense Department talks about drones that can “perceive, analyze, plan, react, and make decisions without human intervention,” which could come out as early as 2030.

The rise of U.S. investment in cyber security has recently come to light with the Edward Snowden leaks detailing the invasive NSA practices which operate on the idea of “security by obscurity.”

As technology rapidly progresses, the distinctions between national security and national defense have become difficult to legally or morally define. However, the U.S. continues its national security policies under the premise that the best defense is a good offense.

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