Sun Tzu is saying that it is generally not a good idea to try to besiege a city that is protected by walls, because it will take a long time and require a lot of resources to do so. He is saying that it is better to avoid this situation if possible, because the preparation and execution of a siege will take a minimum of six months, and it may not even be successful in the end. Sun Tzu is emphasizing the importance of being efficient and conserving resources in military operations, and he is warning against taking on unnecessary challenges that may not lead to victory.
The rule is, to avoid taking on projects that require a lot of time and resources without a clear guarantee of success.
It is important for a company to avoid taking on projects or initiatives that will require a lot of time and resources without a clear guarantee of success. Just as a military commander must carefully consider the costs and benefits of launching a siege on a fortified city, a business leader must carefully evaluate the potential risks and rewards of any major undertaking. By avoiding unnecessary or overly ambitious projects, a company can conserve its resources and focus on more promising ventures that have a higher likelihood of success. In this way, a business can avoid wasting time and money on efforts that are unlikely to yield a good return on investment.