That's a pretty naive position and by its definition one shouldn't trust any government on earth.
Government exists to provide glue for societies when individual motivation is insufficient or harmful.
These situations are generally pretty serious (national health crisis, economic failures, intelligence, war) and thus require triage.
"The first casualty when war comes is truth" isn't actually pointing to an absolute devaluing of truth: it's noting that suddenly there are many other goals that people perceive as more important than truth. E.g. preservation of national sovereignty, prevention of casualties, maintaining civil morale, etc.
Most wars would not be fought if governments were trustworthy. And those that remain could be fought with full transparency.
Trust is everything in society. When you start making exceptions everything falls apart.
I wouldn't ever be able to trust a govt org again if it was revealed they'd made the decision to deliberately lie to their populace. There are few things that a government can do which is unforgivable, and brazenly lying to the faces of its citizens is one of them.