Investing in defense may be a good choice for investors. It can be exciting to own shares of multinational conglomerates whose products are used by militaries across the globe. Investing in defense can also help investors be more in tune with current events; it can also add useful diversification to a portfolio. Another advantage is that the defense industry is generally cyclical and defensive, with more dividends than growth. There are many ways to invest in defense.

Here are the 6 largest US defense companies. Defense giant United Technologies (UTX  ) was founded in 1934. United Technology is part of the Dow Jones Industrial Average. According to Morningstar, it currently has a market capitalization of $82.9 billion and yields 2.61 percent. United Technologies is known for its missile and aircraft systems and Otis elevators.

The multinational industrial Boeing (BA  ) was established in 1916 and operates commercial, technological, financial, and defense divisions. Boeing is part of the Dow Jones Industrial Average. It currently has a market capitalization of $78.9 billion and yields 3.23 percent. The President's aircraft, Air Force One, was built by Boeing. Its F-15E Strike Eagle is a favorite of the US Air Force.

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The aerospace and advanced technology giant Lockheed Martin (LMT  ) was formed through a merger between the Lockheed Corporation and Martin Marietta in 1995. It currently has a market capitalization of $73.3 billion and yields 2.68 percent. Lockheed Martin is known for its F-35 Lightning II fighter program, controversial due to design and cost concerns. 

The defense company General Dynamics (GD  ) has roots dating to 1899 and operates aerospace, combat systems, marine systems, and information systems segments. It currently has a market capitalization of $40.9 billion and yields 2.11 percent. The conglomerate is known for its M1 Abrams tank and Stryker Interim Armored Vehicle.

The weapons and electronics company Raytheon (RTN  ) was founded in 1922. It currently has a market capitalization of $39.5 billion and yields 2.06 percent. Its guided missile and intelligence and information systems are renowned and used by organizations including the National Aeronautics and Space Administration and the Missile Defense Agency.

The defense company Northrop Grumman (NOC  ) was formed by a merger between Northrop and Grumman in 1994. It currently has a market capitalization of $39 billion and yields 1.53 percent. Northrop Grumman has made a commitment to hire more veterans in partnership with President Obama's Joining Forces initiative.

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Besides the top 6 in the US, there are international defense contractors and smaller American companies. They include BAE Systems (LON: BA), Airbus Group (EPA: AIR), Leonardo-Finmeccanica (BIT: LDO), Almaz-Antey, Thales (XPAR: HO), Mitsubushi Heavy Industries (TYO: 7011), L-3 Communcations (LLL  ), etc. Another way of investing is an exchange-traded fund (ETF). The most popular defense ETFs are iShares U.S. Aerospace & Defense ETF (ITA  ), PowerShares Aerospace & Defense Portfolio ETF (PPA  ), and SPDR S&P Aerospace & Defense ETF (XAR  ). The first is the most expensive and liquid. As these ETFs track indices with tens of holdings, they are more suitable for investors who dislike stock picking but are willing to pay expense ratios for broader exposure.

Investing in defense has advantages: decent dividends and low-medium volatility. But profits from war and death may be morally objectionable. Thus defense, like alcohol and tobacco, will be avoided by socially responsible investors. Another disadvantage is that defense stocks seem pricey currently, and future governments might cut defense spending to reduce deficits. Investors have much to consider.

The author does not hold any positions in any of the stocks above.