Do I need to disclose upcoming training during a job interview?

I would not share that information. Life happens. Planning to go to BCT in Jan doesn't mean it is a done deal. You could lose a job opportunity for no reason. If you are offered a position, you can decide whether or not to have that discussion when you give them the response about the offer.

I would tell them, in my opinion if you deceive an employer during the hiring process you will always carry a black mark in the employers mind. If the employer is not willing to hire you because of pending Military service then the employer is probably willing to fight rehiring you under the Uniformed Services Employment and Reemployment Rights Act (USERRA) because the USERRA also requires that service members provide advance written or verbal notice to their employers for all military duty unless giving notice is impossible, unreasonable, or precluded by military necessity. An employee should provide notice as far in advance as is reasonable under the circumstances. They will argue that if you knew when you were hired then it was reasonable for you disclose at that point. They will probably win at Dept of Labor. For most companies it won't matter unless they are a small company hiring you for a one deep position and large companies like to boost about their hiring programs for Reservists/National Guardsman.

You only need to inform your employer of periods of non-availability. If you are interviewing for a job, they are not your employer, therefore: none of there damn business.