Never try to take a fortified hill
There is s couple of ways to look at this. When a competing company has executed a “crossing the chasm” strategy in a market, then this market can be considered a fortified market.
Never try to take a fortified hill, especially if the Army on top is bigger than you are.
William Redington Hewlett
In a competitive market companies tend to react to what the competition does. “When they renew their software so should we”. This can lead to trend behavior. It is unwise to try to enter a market in which everyone has recently renewed their software.
I have had an experience with the technical wholesale industry in the Netherlands. This industry has a lot of companies. These companies are all linked to 3 large purchase organizations. These companies have either bought a software company or have a development team in place. Members are sort of obligated to use that software. This can be considered a fortified market.