Succinctly, they are:

1) Lots of mergers and acquisitions (M&A) activity in the sector (for example, Northrop Grummans $7.8 billion buyout of aerospace company Orbital ATK)

2) The prospect of more U.S. troops being deployed to the Middle East

3) Strong sector fundamentals

4) The passing of a $700 billion defense bill by the Senate for war spending and the production of 94 F-35 Lightning II jets.