In a worst-case scenario involving a Chinese type lockdown...
It takes a maximum of 14 days to show symptoms of coronavirus, but most people will start showing symptoms after 2-5 days.
If the lockdown starts on day "1", after a week the military can go door to door to check for symptoms, those that show symptoms can be quarantined, the process takes about a week and is repeated after 14 days. This would mean that no additional spreading would happen after day "1" and all cases would be identified (and the lockdown could be lifted) on day 21.
I believe this is basically what China did in Wuhan. There are some videos on twitter of empty highways, and videos of pretty brutal police actions against Chinese citizens.
I don't know if this is something western (civilized) countries would be willing to do. It would involve removing ~all freedoms from citizens for three weeks.
Military-style lockdowns work. The problem is politicians do not have the balls to do them.
Sooner or later they will capitulate and agree to have a global military lockdown.
I suspect they will close the stock markets soon, keep the essential utilities/banking/health care services and food deliveries running as long as they can.
Without strict lockdown, in some projections, half of the global population will be affected.
Failure to understand the exponential function will lead to inaction or late response.