What kind of development model do you think it is appropriate to use some military software systems?

An incremental model or a helical model can be used in a personal opinion.

The incremental model can build up the component gradually, the software architecture design is open, and the new software component is simple and convenient, so the military personnel can have more time to study and adapt the product.

And for the incremental model of software architecture design is open to this feature, the military should be highly confidential to not allow hackers to crack.

Although the spiral model is more risky, but for the military's ability compared with other large enterprises more capable and funds to manage the development of software, in the case of high-level confidential development of the large-scale projects, although each cycle has a large number of risk analysis process to facilitate timely cessation, a risk-driven advantage, But the military's software development is difficult to find competitors, regardless of commercial risks, can be fully invested in the development of software, to make a large-scale software in line with military intentions.

What kind of development model do you think it is appropriate to use some military software systems?