Special rule for 1805 Campaign:
As long as this condition is not met. No other Coalition action may be undertaken ...
On the first turn it is possible for Napoleon to reach ULM.
Since the coalition cannot do anything else except besiege Ulm & Mantua. The French could sit in ULM, blocking the siege using Napoleon, while the remainder of the French forces move about Europe totally unmolested. Cleaning up Italy, Portugal etc.
They could even attempt to force the Channel crossing as England would be unable to reinforce the lone fleet that is defending the channel.
Should this instead read:
No other Austrian action may be undertaken..