Will my iPhone 6 (Model A1549) work in Japan?

I'm in the military and PCSing to Japan. I bought a brand new iPhone 6 a few months ago prior to being notified I was going to be stationed in overseas. Currently, I'm with AT&T and am hoping to get my iPhone unlocked before I leave and then I hope to be able to use it with Docomo SIM card. That way, I won't have to waste or spend extra money for another phone over there. Plus, I don't want to give up a good phone I just got not too long ago. I looked at the LTE compatibility chart on the apple website and according to that, the model I have that AT&T gives to its customers won't work with Docomo in Japan. But from my understanding once an iPhone is unlocked, it could essentially be used for any other company. So if I get my iPhone 6 unlocked, I could use it for Sprint even though Sprint isn't listed under the supported U.S. LTE networks for the model A1549. And if I can get it working for Sprint, then I can get it to work for Docomo in Japan too right? (Sprint sells the iPhone 6 model that is compatible with Japan's Docomo) Correct me if I'm wrong because I'm not entirely sure and I need clarification.

All iphone 6 models operate on LTE band 1 so they'll work in Japan if unlocked. You can go with Docomo, but I'd check out bmobile's offerings first since they are cheaper and operate on docomo's network.

http://www.bmobile.ne.jp/

Do check an independent source (for example, Amazon comments) before buying something from b-mobile, because even though they use the docomo network for the cellular part, it's their own Internet infrastructure behind it, and they sometimes do funny things. For example this one:

http://www.bmobile.ne.jp/bmsim/index.html

You wouldn't know from the page, of course, but in fact they limit the speed dramatically, to the point that this offering is nothing short of a scam. I wish I had read those before buying it:

http://www.amazon.co.jp/dp/B00QQ4GS3M/

Unfortunately, your model only supports LTE in the US, Aruba, Bahamas, Bolivia, Brazil, Canada, Cayman Islands, Chile, etc... but not Japan or any of the south-east Asian countries. While it doesn't support LTE, you can still use 3G so there's that.

Only the A1586 work with other countries' LTE networks.

Most of the major cellular companies operate off of A1549 so that you can't use LTE on other networks, aside from sacrificing LTE ability. It's a cash-grab by major cell companies in the U.S. and is quite sad, but at least you have 3G...

Poster above is wrong. All iPhone 6 models support the LTE bands in use in Japan.

https://www.apple.com/iphone-6/specs/

This list seems to be incomplete: https://www.apple.com/iphone/LTE/

From what I gather, it only lists the carriers which officially support the model in question, but many people report that as long as the bands match, it will work anyway. See for example here: http://forums.macrumors.com/showthread.php?t=1835927

I first checked that Apple site which caught my curiosity, and I later called Verzion (my then provider). They said the 3G would work, but they would not provide any promises about LTE functionality.

You may be able use that version, but keep in mind the fine print that Apple mentioned about band coverage "LTE band support is based on iPhone model number and configuration for either CDMA or GSM networks. LTE wireless service may not be available even if listed bands are supported by your carrier."

Apple's official compatibility site is notoriously misleading, as it lists "supported carriers" when they really mean "officially supported carries". It's a small difference, but in practice it means that the hardware is compatible but may not work on a specific carriers anyway. Verizon in particular has (had?) a much maligned policy where they'll support phones that were originally activated with Verizon, but blacklist phones activated on other carriers despite them being identical, unlocked models.

As for Japan, virtually all iphone 6 models support the major LTE bands necessary to work on the local carriers. And as long as you're phone is unlocked you'll be able to find a carrier to operate on (i.e. docomo, softbank or one of either of their mvnos).

I was in Tokyo this past Christmas and New Years holidays. I'm with AT&T and my iPhone 6 is unlocked. It worked just fine but lags a bit. AT&T models are GSM locked, the Verizon one is CDMA unlocked but GSM compatible however, international use is still limited to certain bands for the same model. Honestly an A1586 (ip6)/A1524 (ip6+) would work better. Worst case scenario you can sell your phone in Akihabara/craigslist/ebay and get one with the carrier you're gonna subscribe to or buy a Japanese compatible one at the used phone stores in Akihabara. Important to note that you should be prepared that not all carriers in Japan will activate service right away once you subscribe, even pre-paid service, sometimes it take a few days. Have a backup phone plan. I signed up for the $30/month limited voice and data plan, no contract, with AT&T before I got there until I got settled in. Or you can rent a phone at the airport.

I always sell my old phones and right now iphone 6 is still fetching a decent price on ebay if you decide later you want to go that route.