When you're getting married and are in the military, the marriage laws are a little different than for those in civilian locations. If both couples are U.S. citizens and want to get married in the United States, then the process is the same as normal. If you want to create a prenuptial agreement, then you still need to reach out to your attorney to do so.
However, if someone is a foreign national, then there are more challenges that you'll need to address. The marriage has to be legal in the country where it's going to take place; in some places, it might be required that the bride and groom's parents both agree to the marriage as well. In some circumstances, service members need to get the approval of their commanding officers before they can get married.