What did reagan launch the largest peacetime buildup of in american history?

The Reagan missile defense system dubbed  the star war program

The Strategic Defense Initiative (SDI) was a proposed missile defense system whose intention was to protect the USA from ballistic missiles attack both submarine  launched and intercontinental missiles. It was dubbed unrealistic but the USA has continued to improve it  even after the fall of the soviet union.

Ibelieve the correct answer is d.