Hmm. Watch out, more numbers.

Trying to take into account those and other factors of war besides being shot in battle led me to this statistical estimate of the effect of the Iraq War. The lowest bound was 400,000, and treating excess mortality as happening on the average between 16 and 67 (an overtly optimistic hope that people under 16 remain the least affected-by-war group), we get 10.2 million expected life years lost. Assume that for every person killed, there is one person disabled in some way (a quick check suggested 3:1 serious injury:death ratio for soldiers and 1.8:1 for civilians, I went with 1:1 because disability doesn't always follow from serious injury, but concerns like PTSD can bring the ratio up to equal) and the figure is just above 20 million DALYs lost to the Iraq war. GiveWell's figure of $100 per DALY being the upper bound of efficient charity means that a lobby group or charity that could have stopped the Iraq War given 2 billion dollars would have been a gold-standard efficient charity.

I believe this answers your query, Nancy. Stopping wars most definitely rates as some of the best charity around.