There are examples of complex systems created in a short time:
1. Manhattan project: The Hiroshima bomb was only tested once. The Nagasaki bomb was a different kind and never tested in advance. The whole infrastructure to produce those bombs was created from scratch within three years.
2. ICMBs: It required to shrink down nuclear bombs to put them on rockets, develop the capability to steer rockets precisely enough over thousands of kilometer, create a whole industry around the manufacturing. Then scale it up to hundreds of rockets.
3. Put a man on the moon. Nobody died at the first attempt.
You could consider those three steps as an example of Gall's Law as they build on each other. However, I would say each of them is a complex system in itself.
I would argue that none of these things are complex systems, in the systems theory sense. A complex system is typically comprised of a network of casual relationships so deeply interconnected that its behaviour is not easily reducible (in the scientific sense of isolating individual behaviours to be examined). Human designs intentionally avoid this and instead strive for mostly linear causality, precisely so we can test and develop individual parts in isolation.
