I am currently developing a battle field simultation engine from scratch (ok, almost from scratch), as a C++ learning project, and for use as a portfolio when applying for jobs. My goal is to become an engine developer working with large scale environments, including massive object counts, realistic physics and challenging AI.
The specific aim of the project is scenarios like the ones used by the Total War series, albeit without the graphics and with some reduction to the number of features (at least until I get the basics up and running).
I am basing this on my Masters Thesis regarding Bounding Volume based collision detection in large scale environments similar to the ones from the Battlefield series. Along with my thesis, I created a basic physics engine in java (source included in the link above), and currently, I am moving this to C++, both to learn the language, and to be able to base the engine on this.
More info will follow in time, when I get the basics up and running, and when I learn how to use this journal properly.