Once engaged in secret research, he was naturally far more circumspect.

Most probably, the base was built in order to do secret research.

India exploded what it called a "peaceful" nuclear device in 1974 after years of secret research.

It was once devoted exclusively to secret military research.

There are also concerns that Russian military scientists may still be conducting secret research on biological weapons.

When so much secret research was going on, such accidents were bound to occur.

They became a conduit for information between researchers who were sequestered in secret research.

In the 1970s, the base's mission shifted to top secret research.

A nuclear trigger is hardly top secret research, even I could probably build one based on open knowledge.

When this claim proved to be false, the focus shifted to the role of Universities in secret military research.