The US Navy's submarines, equipped with nuclear power propulsion engines and state-of-the-art weaponry, can silently operate around the world and attack any target with devastating force if called upon to do so.

With around 70 boats in service, the force consists of Ohio-class ballistic missile submarines (SSBNs), Ohio-class guided missile submarines (SSGNs) and attack submarines (SSNs).

The attack submarines include the Los Angeles class, the Seawolf class and the Virginia class.

All US Navy submarines utilize nuclear power, which provides speed, endurance, mobility, stealth and payload, helping the US Navy to maintain its "preeminence in the undersea battlespace," according to Submarine Force, US Pacific Fleet.

Because their nuclear reactors do not need to be refueled in a 25-year life span, the submarines have nearly unlimited endurance, according to the US Naval Institute.

This allows them to complete missions at home or across the world limited only by consumables, such as food.

Nuclear power also affords unmatched stealth for the US submarine force. Unlike diesel-electric submarines that must snorkel frequently to clear the exhaust from their diesel generators, submarines powered by nuclear propulsion are independent of air and have no need to snorkel.

Because of this, they can maintain maximum stealth by staying completely submerged, reducing their vulnerability.

Nuclear propulsion also maximizes speed.

"The nuclear reactor on board a submarine allows it to operate at high speed for long periods of time with unlimited range," according to the institute.

"In comparison, diesel submarines operate using electric batteries and can only remain submerged for a few days at slow speed, or a few hours at top speed."

The Ohio class

The US Navy has 14 ballistic missile submarines or SSBNs, known as "boomers."

Designed for stealth and the precise delivery of nuclear weapons, "boomers" are specifically made for extended deterrent patrols, and make up one leg of the US nuclear triad, which also includes land-based intercontinental ballistic missiles (ICBMs) and long-range bombers.

Each SSBN can carry 20 Trident II D5 missiles, inertially guided missiles capable of carrying multiple warheads and launched by the pressure of expanding gas within a launch tube, according to the US Navy.

After launch, Trident missiles are capable of re-entering the atmosphere at speeds of up to Mach 24 and have a maximum range of about 7,500 miles (12,000km).

Meanwhile, the Navy's four Ohio-class guided missile submarines, or SSGNs, provide it with "unprecedented strike and special operation mission capabilities from a stealth, clandestine platform," according to the US Navy.

Each SSGN carries up to 154 Tomahawk land-attack cruise missiles and is equipped with four torpedo tubes to launch Mk48 torpedoes.

The Tomahawk, a subsonic cruise missile with long-range, deep strike capability, has a range of up to 1,550 miles (2,500km).

It carries a 1,000-pound (453kg) warhead, according to the US Department of Defense.

The Mk48 is a heavyweight, acoustic-homing torpedo with a range of up to 25 miles (40km), a 650-pound (294kg) warhead and a speed of up to 30 knots (56 km per hour).

Attack submarines

The US Navy additionally has about 50 attack submarines in service, also known as fast attack submarines.

These are designed to seek and destroy enemy submarines and surface ships; fire cruise missiles; carry out intelligence, surveillance and reconnaissance missions; support battle group operations and engage in mine warfare, according to the US Navy.

The newest class of attack submarines, the Virginia class, features innovations that provide improved shallow-water ship handling and delivery of special operations forces, according to the US Naval Institute.

It incorporates the latest in stealth, intelligence-gathering and weapon system technology.

A Virginia-class submarine can fire vertically launched Tomahawk missiles, Mk48 torpedoes and UGM-84 Harpoon missiles.