[SJackson]

The pentagon spends a lot of money, making some companies rich and employing hundreds of thousands of people in industry. There are lots of forces at work shaping their budget, not all of them involving military strategy.

Even a General may need a job when he retires.

[ConsistentLibertarian]

And politicians have to make sure that companies in their disctrict get big contracts with the Pentagon, or keep contracts, or bases. The political forces are no different than they would be if you had the government paying out hundreds of billions of FDR style public works projects.