There were two major peaks of defense spending in the 20th century: World War 1
It was an "military" expedition, one of many made by Europeans to recover the Holy Land from the Muslims.
A set of laws, passed in the midst of fierce wrangling between groups favoring slavery and groups opposing it, that attempted to give something to both sides. The south gained by the strengthening of the fugitive slave law, the north gained a new free state, California. Texas lost territory but was compensated with 10 million dollars to pay for its debt. Slave trade was prohibited in Washington DC, but slavery was not.