Marriage, in itself, is challenging, but when you throw one of the spouses being a police officer into the mix, it takes on a whole new set of unique challenges that must be overcome in order for the marriage to work. Speaking from experience and having been in a wonderful marriage for the last 23 years with a member of law enforcement, you can consider these words as coming from an "expert."
You must expect your spouse to miss many holidays and other important family functions that a normal husband or wife would not. Seeing as the criminals don't take holidays, then neither do those who protect us. And being their spouse, it is important to swallow your disappointment, and try to be as understanding as you can. Perhaps, schedule the Thanksgiving dinner to be held on their day off, or open gifts on Christmas Eve if he or she is lucky enough to be off that evening. Be as flexible as possible around their schedule and they will be very grateful to you. They carry enough guilt around at missing these events anyway, and the more you can do to reassure them that you understand, or rearrange your schedule, then the happier you both will be.
Shift work is also challenging. They work nights, evenings, and weekends. It usually takes many years on the job until they are Senior enough to be given the day shift with weekends off. It's not uncommon for police officers to marry nurses, doctors, paramedics, or emts, people like themselves who are familiar with the idea of working shifts and holidays. Having worked in similar area's helps you to be more empathetic when you can't be there for your little one's play at school, or you try and make sure one of you makes it if the other one is working that day. Cooperation and flexibility are key in managing raising children and running the marriage.
Be a good listener. Police officers see horrible things on a day to day basis and keeping those things bottled up inside is not good for them. Sometimes they are able to talk to their fellow officer's about what they deal with, and, like people in the medical field, they develop dreadful senses of humor in an effort to help them cope with the atrocities that bombard their senses. Graveyard humor is very common among law enforcement personnel and if you happen to hear a police officer laughing at a horrible accident scene, he or she is not being insensitive, it is just a coping mechanism that they have developed over time or they would not be able to deal with the things they deal with day after day. If your husband or wife wants to talk about their day, try to listen. You will develop a better understanding of what they go through, and it will help you both become closer. If you don't, you will run the risk of them turning to someone else for the comfort they so desperately need.
Unfortunately, the divorce rate among police officers is 60 - 75%, while the normal population's is 50 %. All of the things listed above contribute to that elevated rate, but they also face a lot of temptation on the job. Let's face it. There is something about a man in uniform, dripping testosterone, coming to your rescue, which many women find very appealing. Many police officers are propositioned on the job and offered sexual favors. If their marriage is a strong one, and they know they have a loving, supportive spouse at home, then those temptations will be much easier to say "No" to. Once a fairly average man puts on that uniform, he suddenly transforms into a superhero into a lot of women's eyes and they don't care if he is married or not. Sad, but true. And it happens not only to the guys, but the women, too.
The single, most important thing that may differ from a "normal" marriage is before your spouse heads out that door for their shift, be it days, evening, or nights, please tell them you love them. It may be the last thing you say to each other. You never know if they will come home when their shift is over. Love them like they deserve to be loved.