Sun Tzu has become an internatonally much-respected military theorist during the past decades, as a consequence of English translations of his ancient writings.
The respect for his work and the apparent universality of some of his remarks (or to be more specific: The applicability of the interpretations of his remarks to modern problems) has its problems, though.
One example is the issue of urban warfare (OHK in German). Urban warfare was a very popular topic during the 90's up to the COIN fashion of about 2005-today.
Sun tzu was often cited in regard to the problems with urban warfare. The Russians had demonstrated those problems anew with their debacle in Grosnyi '94.
The relevant parts of Sun tzu's known writings are
"If troops lay siege to a walled city, their strength will be exhausted."
"Therefore, the best warfare strategy is to attack the enemy's plans, next is to attack alliances, next is to attack the army, and the worst is to attack a walled city."
"Laying siege to a city is only done when other options are not available."
"If the general cannot control his temper and sends troops to swarm the walls, one third of them will be killed, and the city will still not be taken."
"This is the kind of calamity when laying siege to a walled city."
"Therefore, one who is skilled in warfare principles subdues the enemy without doing battle, takes the enemy's walled city without attacking, and overthrows the enemy quickly, without protracted warfare."
"Generally, the principles of warfare are:
there are walled cities not to be besieged;
(quote from here)
It's impossible to produce a perfect translation. Every translation, even every reading of ancient texts should be taken with a grain of salt.
Well, now a bit about the city topic: The Chinese had no elaborate siege technology during the time of Sun Tzu. Sieges against properly fortified ("walled") cities were pretty much attempts to starve the defenders. Such attempts were very risky and slow up to the late 19th century because of poor hygiene and logistical capabilities. It's quite likely that more soldiers /warriors died on average due to illnesses than due to fighting in historical sieges.
Sun Pi wrote his treatise on the art of war not long after Sun Tzu and didn't have such an aversion against sieges.
Why? Simple; the Chinese had developed techniques to overcome fortifications.
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The urban warfare theorists of the 90's had a huge aversion against or great fears about urban warfare (for many good and not so good reasons) and some were happy to call upon Sun Tzu as reinforcement of their position.
That was of course utterly pointless because his remarks had been turned around many times over in the meantime.
Such is the risk of trusting old treatises on war.