We are planning on a military pension, which helps a lot, and we will likely own at least one managed rental property which by then should have a very nice cash flow. Also (and I know this is controversial), we will likely have a high 6 figure, conservatively, inheritance coming to us at some point. I know, I know, anything can happen, but given the situation, it's extremely unlikely that anything will happen to wipe out most of that. Of course, our hopes are that it won't come to use for years after we retire. And we are working to have a paid-off house. I know that's not always ideal, but given our situation, we think it's the right choice for us, and it will mean we have a mostly free place to live
Additionally, we invest in regular, taxable investment account. These accounts are all mutual funds and I've attempted to optimized tax-efficiency, but it did make my head spin a bit and I'm sure a pro could do a bit better.