What and when did US Army brass know about Maj. Nidal Hassan’s extremist views and his ties to a key jihadist cleric — and why didn’t they act before he gunned down 13 soldiers at Fort Hood six months ago? It’s a simple question — and a very significant one, to boot. But neither the Pentagon nor the Justice Department wants that information made public. Which is why the two top senators on the Homeland Security Committee — Joe Lieberman (I/D-Conn.) and Susan Collins (R-Maine) — have subpoenaed stonewalling Defense Secretary Robert Gates and Attorney General Eric Holder. “We have...