A search and rescue of chemical-weapons casualties aboard a U.S. Navy vessel, a helicopter assault on Fort Irwin and an antenna that looks like an inflatable beach ball. What do they have in common?

Marine Expeditionary Units which brought urban combat to 3 states over nine days.

How Marines get in a RUT
Marine Expeditionary Units like the 13th and 26th provide a sea-based rapid-response force all over the world. These task forces are called on for crisis response, reinforcing embassies, amphibious and other operations, as well as humanitarian aid, supporting evacuations and disaster relief.

In Realistic Urban Training (frequently called RUT) they're taken out of their comfort zone, often placed in unfamiliar environments and required to overcome a series of realistic challenges that they may encounter in combat. It involves a combination of aviation, ground combat and logistics applied to urban warfare, meant to prepare the “Fighting 13th" for deployment this fall to the western Pacific.

These exercises give them an opportunity to refine individual skills -- close-quarters battle training, for example, using explosives to breach doors and non-lethal and live fire.

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During the tasks, Marines also get the chance to work on small unit tactics through to company and higher-level command and control.

To succeed in this exercise, the unit must combine command, air, ground and support assets to perform a wide range of missions, from combat to humanitarian assistance:

*    In California, Marines and sailors conducted a helicopter assault exercise on Fort Irwin last week. Also in California, the 13th Marine Expeditionary Unit's Maritime Raid Force conducted a night raid.

*    In St. George, Utah, Marines set up a forward arming and refueling point at St. George Municipal Airport. Those points are essential in combat; they provide re-fueling and resupplying to military aircraft as well as crucial aircraft maintenance.

*    At this Utah training site, dramatic high-pressure scenarios are played out such as conducting a long-range helicopter-raid. Challenges involved rotary-wing Ospreys, Super Stallions, Hueys and Super Cobras, as well as fixed-wing Harriers and Hercules planes. For those in the neighborhood, the Marines have welcomed civilians to watch their military exercises and aircraft from outside the airport area.

*    In Arizona at Yuma Proving Ground, Marines with the 13th MEU Maritime Raid Force parachuted at night from approximately 3,000 feet, landed and conducted a night raid.

Taking GATRs to war
The Fighting 13th will be the first MEU to bring state of the art GATRs with them on their western Pacific deployment in 2013.

The GATR, or Ground Antenna Transmit Receive, is an inflatable satellite antenna that uplinks with satellites and provides secure and unsecure Internet access. The system will allow them to rapidly transmit and receive data on operations.

Lightweight and compact, the GATR system replaces the 13-ton Phoenix Tactical SHF Satellite Terminal, which requires a generator trailer and two vehicles. GATR requires only six “pelican” cases and can be set up within an hour.

Defeating chemical weapons at sea
With the constant threat of Syria unleashing chemical and biological weapons, what if a U.S. Navy vessel was attacked by this threat?

In complete darkness aboard the USS Kearsarge (LHD 3) at sea, a search and rescue was conducted amidst the threat of a chemical weapon by the 26th MEU last week.

The 26th is deployed to the 5th Fleet area of operations aboard the Kearsarge Amphibious Ready Group.

With their special training in chemical, biological, radiological and nuclear threats, they took on tasks such as finding a hidden casualty in a hazardous environment, treating the victim and extracting to the designated safe zone.

Over the course of three days, they tackled tough rescues in confined spaces – often with cumbersome heavy CBRN gear and self-contained breathing apparatuses. A chemical environment means the Marines wear “Level B MPP suits” (short for Mission-Oriented Protective Posture), gear that protects them from threats.

Teams took off from the hangar bay to tackle the challenge of navigating the realistic obstacle course in this exercise.

Marines had to overcome trip hazards like chains that are used to secure the vehicles to the ground, quad cons, tight corridors and tight spaces between Humvees, all while searching and extracting the victim.

While grappling with the terrain, the Marines also had to contend with searing temperatures and humidity often in darkness with bulky tanks on their backs in cumbersome protective clothing.

Ballet dancer turned defense specialist Allison Barrie has traveled around the world covering the military, terrorism, weapons advancements and life on the front line. You can reach her at wargames@foxnews.com or follow her on Twitter @Allison_Barrie.