If you have your permanent residence, you can apply for citizenship as the spouse of a US Citizen once you've had the green card for 2 years and nine months, and have lived in the US for at least half that time.
Qualified military service members and their spouses may receive expedited processing of their naturalization applications. Some requirements (such as physical presence in the US and length of permanent residency) may be waived or shortened.
You may want to check whether you qualify as a spouse of a military service member. Read the M-476, A Guide to Naturalization, and M-599, Naturalization Information for Military Personnel, to see if you qualify. The publications are from USCIS and available for free at http://www.uscis.gov/natzguide .
Even if you are not a spouse of a qualified service member, the Guide to Naturalization should provide you with the answers to basic questions about naturalization.
Prior to becoming a citizen, you must first become a lawful permanent resident. You stated that you have been in the U.S. less than two years. How you entered the U.S. will dictate what process you will need to use to become a permanent resident. If you you entered without inspection, you will likely have to leave the U.S. and re-enter after having your marriage approved and a waiver granted. If you entered using a visa and received an I-94 you will be able to file for adjustment of status with CIS.
Please consult with an immigration attorney prior to embarking on any path regarding your status.
I am not clear from your question whether you have already applied for your greencard, and if so, if your husband continues to be in the Navy. Depending upon your situation, you may be eligible for an expedited form of naturalization. However, if you have not yet filed for your permanent resident status (greencard) you will need to do so first. You may wish to consult with an immigration attorney to discuss the specifics of your situation.
I am surprised by the extent to which the other answers above have ignored the information you posted, as you stated clearly that you are already a Conditional Resident, that you have been married for four years, and that your husband was in the US Navy.
The first and most important deadline to note, since you have been in the US for less than 2 years, is that you must file the I-751 Petition to Remove Condition of Residence on time, i.e. within the 90 days before the 2-year anniversary of the date you were granted Conditional Residence, otherwise you lose your resident status.
The next thing to note is that as the spouse of a US citizen you are eligible to apply for citizenship after you have been married to that person and living with them as a permanent resident (including as a CR) for three years. So, on the 3-year anniversary of the grant of conditional residence (at which point your I-751 petition may still be pending, and probably will be), you will be eligible to file for naturalization.
The most important thing to note is that if you are scheduled for a naturalization interview while the I-751 is still pending, the naturalization examiner has the discretion and authority to adjudicate both applications at the same time... your I-751 does NOT need to get approved before you can apply for naturalization!
Naturalization through military service under INA Section 328 is a red herring (irrelevant), as your husband is already a US citizen. However, you may take advantage of INA Section 319b - This means that if your husband was on active duty in the Navy in Japan, and your Conditional Residence was intially granted while you were still in Japan, then that time counts toward the 3-year total time as a green card holder that is required for you to be eligible to apply for citizenship - as the spouse of a US citizen who was on active US military duty, the physical presence requirements in the US do not apply to you.