MONEY, MEET MOUTH. It doesn't involve invading anyone, or kicking any ass that's evolved beyond the microbe stage, but if we could spur the pharmaceutical companies or the NIH to put a bit of money into the anti-HIV microbicides currently nearing breakthrough status, we'd save a lot of lives. As Kate Steadman points out, the primary driver of HIV infection in the third-world are patriarchal sexual arrangements where a lone male, with his many wives, mistresses, and prostitutes, can contract HIV from one source and spread it far and wide.
Sadly, condom use is taboo under the best of circumstances and, thanks to funding and support from the Christian Right, officially discouraged in many countries (like Uganda). An anti-HIV microbicide would give women a discreet way to protect themselves, one whose application and use they could largely control. Unfortunately, poor women in third world countries command neither financial power nor international attention, so there's been precious little economic investment designed to bring these microbicides to fruition and distribution. If we were nearly as serious about humanitarian projects and women's rights as we claim, that wouldn't be the case.