It’s a sign! “NCIS” on CBS has been the No. 1 show on Tuesday nights for four weeks. It is the highest rated show on TV. Why is this important except for advertisers who want to sell products?

It is important because America is choosing to watch Special Agent Leroy Jethro Gibbs catch “dirtbags.” It’s a cop show, you may say. Yes, but these cops are in the Naval Criminal Investigative Service. They solve crimes involving Sailors and Marines. So for one hour every Tuesday (2 hours if you count “NCIS-Los Angeles,” the spinoff) we are in the world of the United States Navy and Marine Corps.

There are many reasons to watch the show. It is face paced, clever and the audience is drawn into this team with all its unique characters. They are a family and we want to be one of them. They have talents we wish we had and they use them for good.

Special Agent Tony Dinozza (Michael Weatherly) is the goof off from every office we’ve ever worked in. But he is a former cop and relies on his instincts to come up with that one idea that might solve the case. Of course, he is also a great shot and a good fighter which comes in handy with bad guys.

Special Agent Timothy McGee (Sean Murray). He is the geek in the office. We know we need him but we can’t figure out what he is doing on the computer. But we pretend we do like Tony. In an increasingly technological world he is the hacker of choice. He is also a good field agent and can shoot as well as the rest of them. I like him especially because he is a best-selling author who wrote a book loosely based on his team mates.

Forensics Specialist Abby Shuitto (Pauley Perrette), a goth with a master degree in Forensic Science, finds that impossible bit of DNA or chemical compound that solves the case. When all the others have to keep their cool, she is the emotional outlet for all of us. Alone in her lab she plays music, sings, talks to her machines and yells.

Officer Ziva David (Cote de Pablo)… After last night’s episode I think we can call her “Special Agent.” A former Mossad agent with Daddy problems, she had the task of joining the team after the death of Special Agent Caitlin Todd by Ari the terrorist who turns out to be her half brother who she had to kill to save Gibbs (a little soap opera). I love her character. She is tough, complicated very capable and wounded emotionally. And she wears her Star of David around her neck for all to see.

Dr. Donald Mallard or “Ducky” (David McCallum), the medical examiner who talks to the corpse. I’ve learned a lot of stuff listening to his digressions into history. He is the symbol of integrity and honor. His work is to find out how the victim was killed so he can help the team catch the killer. But he never forgets the specimen in front of him was once a living human being who has a family and friends who loved him.

Special Agent Leroy Jethro Gibbs (Mark Harmon), the Special Agent in charge of the team. I left him for last because he is the embodiment of why I think this show says something about America. He is an ex-Marine and fought in Desert Storm. But we learn from him that there is no such thing as an ex-Marine. He is a wounded soul who tragically lost his family. He has seen war and understands those who are in battle now. He knows the truth about the world as he yelled at Dinozzo once, “We are at war and I expect you to fight that war 24/7” His younger team members look up to him and want his approval. He is hard to please. He expects the best. We can all remember a teacher who was really hard on us but whom we appreciated later because we learned to be our best.

One thing Gibbs teaches us is that members of the Navy and the Marines are human like us. But because of their choice to serve we should appreciate the sacrifices and pressures they and their families endure while protecting us. The Navy’s motto is “Honor, Courage and Commitment” and sailors strive to live up to it every day on carriers, submarines and in far away bases. Semper Fidelius-Always Faithful is the Marine motto. Once a Marine, always a Marine. This sense of being committed to something greater than one’s self is what makes this show different and why viewers are drawn to it.

All of this crime fighting takes place on Navy and Marine bases, aircraft carriers, submarines, and the Navy Yard. Sometimes it is just like civilian crime. It could be a jealous husband, wife or lover, betrayed best friends, or criminals turning on each other. But our team knows that any crime involving the military can threaten the security of the United States. Navy and Marine personnel deal with sensitive information everyday. These investigators have to know what is merely crime or something bigger and more dangerous.

There has always been an overt acknowledgement on the show of the threat of terrorism The real NCIS agents deal with anti-terrorism operations. To the real agents and those on the show it is not a “man-made disaster,” it is a terrorist attack. The war in Iraq or Afghanistan is not an “overseas contingency operation.” It is real war and it will go on for a long time even if our approved political vocabulary does not recognize it. We are in danger every minute and this team recognizes it. That is one of the reasons why I believe the show is such a hit.

It is sad that the threat of terrorism is more real on a TV show than in our government. I noticed the other day that Janet Napolitano, our Homeland Security Secretary, had to admit in an interview that there were some people in the United States with al Qaeda leanings that want to hurt us. Duh!!!

But on Tuesday nights, when we watch “NCIS,” we know Gibbs has our back. Semper Fi!