If the U.S. follows through with a military strike on Syria, the weapon of choice will likely be the Tomahawk cruise missile.

Cruise missiles have been used by the U.S. as far back as 1991 in the Gulf War, and as recently as 2011 when they were fired against 20 targets in Libya.

Some of the past missions relied on the Block III Tomahawk cruise missile, which is programmed in advance to strike a specific target and then launched. Today, the Block IV missile is also in use, featuring increased capabilities, including technology that allows it to change course or targets after it has been launched. The Block IV can also hover for extended periods of time before it actually strikes.

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A U.S. Navy official confirmed to Discovery News that GPS technology is used to update the navigation system within the weapon. Still, there are possible stumbling blocks that can cause the missiles to be ineffective.

“There is always the possibility that the intelligence being used is hours or days old, and by that time the target has been moved or human shields brought in to protect the site,” said Michael Eisenstadt, senior fellow at the Washington Institute for Near East Policy. “The Block IV also has its own camera on board to do battle assessment, to see if a re-strike is necessary.”

Although a U.S. Navy official told Discovery News via email that the accuracy level of cruise missiles is proprietary information, Eisenstadt said use of cruise missiles is not an exact science.

“These missiles have a precision level of about five to 10 meters, which is probably as accurate as you need for just about any target,” said Eisenstadt, who also directs the military and securities program at the Institute. “But they do not have a penetrating warhead. Basically it’s just a high explosive warhead like a regular bomb. Tomahawks have 1000 pounds of explosives, whereas penetrating warheads generally have more like between 2000 and 5000 pounds of explosives.”

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There are reportedly four destroyers in the Mediterranean near Syria now, each capable of firing 96 missiles, although not all of the missiles on board each ship are Tomahawk cruise missiles. It is possible the vessels are carrying a mix of Tomahawks, surface to air missiles to be used against aircraft, and ballistic missiles. They may even be anti-submarine rocket launch torpedoes on board.

As for the Tomahawk, once it is launched, its wings fold out during flight, and it can hit a fixed or moving target.

Critics of the proposed mission point out that cruise missiles alone wouldn’t be enough to cause lasting damage to the Syrian army’s elite units. That, coupled with a host of variables and unknowns have caused some legislators to reject the idea of a military strike.

Two U.S. Navy BGM-109C Tomahawk cruise missiles in flight over a mountain range.Getty

Of greatest concern to some are possibilities of collateral damage, especially civilian casualties. Although Syria is known to have amassed large amounts of deadly chemicals, Tomahawk strikes would not go directly to facilities that house the chemicals. Instead, they are more likely to target delivery systems and command centers due to high risk involved in hitting the chemicals themselves.

“The administration has said they’re not going to hit chemical stockpiles so that chemicals don’t get released into the atmosphere,” Eisenstadt said. “There are too many ifs involved with that. The variables include things like wind speed, atmospheric conditions and whether the building you hit falls in on itself. Also unknown is whether the chemicals are stored in the basement or on top floors above ground.”

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As for the danger of civilian deaths, that is another unknown. In the past some missions failed, causing the missile to crash short of its target. That increases the chance of civilian hits. Then there is the possibility of Syria using human shields.

As with any mission, timing is critical. “The bottom line is that we have been telegraphing our intention to bomb Syria, and they have had time to disperse and evacuate various targets we would be likely to hit,” Eisenstadt said.

"If we don’t have the right intelligence, we could be hitting empty buildings. Smart weapons become dumb weapons when you don’t have accurate intelligence.”

Even though the available missiles and technology have limitations, a strike seems imminent to many observers. With Syria suspected of killing more than 1,400 of its own citizens with chemical weapons, Secretary of State John Kerry offered his perspective on a U.S. military response late last week: “Some cite the risk of doing things. We have to ask what is the risk of doing nothing.”