The battle of Kliszów ins an interesting case, because the reason for Saxon-Polish defeat was caused by reasons both political and military. Some would agree that the former played far more important part.

Initially, Polish-Saxon army had obvious numerical advantage and one might argue that with 6500 heavy cavalry on Polish side and majority of Swedish cannons being stuck in the forest (curiously, Saxons and Poles had even more cannons in the camp but for some reason they did not used them in battle) they had also strong tactical advantage. In the early stage of battle, Polish cavalry detachment, consisting of 4 hussar and 6 armored regiments (incomplete, so most likely consisting of about 600 cavalrymen in total or roughly 10% of the entire Polish cavalry force) attacked Swedish mounted units (ryttare, suggesting light cavalry) and forced them to retreat, at least temporarily. Then Poles regrouped and without gathering reinforcements attacked the Swedish infantry, but were slowed by the portable field obstacles (possibly of Frisian horse type, although inconsistent terminology both used in practice and in sources makes it hard to ascertain that) and then halted by massed infantry fire. All ten cavalry regiments withdrew losing roughly 80 people. And this is when the situation became really interesting.

After the unsuccessful attack on the infantry positions, Hieronim Lubomirski, hetman (commander) of the Polish forces decided not to use the remaining troops in the follow-up attack and then simply left the battlefield, because of personal vendetta against the king. This meant that almost 25-30% of the joint Saxon-Polish army (and arguably the best part of it) was not used in actual combat, greatly evening the odds in Swedes' favour. Stopping of the first charge and inaction of the rest of the Polish cavalry, usually well-respected among Swedes greatly increased morale and prompted Swedes to gather the troops and attack the Saxon cavalry ranks. The first attack has shaken the opponent and the second charge, supported by infantry fire resulted in significant losses on a Saxon side. Despite last-ditch efford on the Saxon part, the troops were unable or unwilling to stand against better trained and disciplined Swedes, thus giving the victory to Swedish king.

The delay of Swedish artillery that caused its absence in the actual battle was not a crucial point, as Saxon-Polish forces, despite significant numerical advantage, fielded only 4 or 5 light cannons, what was essentially matched by Swedish 4 falcon guns. Thus, despite one of the early shots fatally wounding Friedrich von Holstein-Gottorp, commander of the cavalry troops on left wing of the Swedish forces, artillery alone could have not decided the course of battle.

Curiously, significant part of the books and articles written about this particular battle focuses on various facets of contemporary tactics while missing one important information, namely why on Earth Polish commander decided not to use 90% of heavy cavalry known to achieve victory in most adverse situations and leave the battlefield what bordered on treason. Historians are still not completely sure what caused Lubomirski to make that decisions but the reason most commonly cited is the fact that he was political enemy of the king August II. Because of the peculiarities of Polish political system using elective monarchy, kings were elected by nobility. After the death of Jan III Sobieski, the two strongest candidates for the Polish crown was Saxon king August II of Wettin dynasty and French prince François Louis de Bourbon, prince of Conti. Although the electional convocation held in 1697 ended with majority of votes cast in favour of prince François, but August II moved into Poland, bribed a significant number of key political figures with the help of two large banking houses and Russian tzar Peter I and then was quasi-legally crowned with additional military support of Peter I who threatened with military intervention should the nobility from eastern part of Polish-Lithuanian Commonwealth hasn't withdrawn their support for the French candidate. After two years of turmoil, August II was finally legally crowned in 1699.

Having secured the crown of Poland, he quickly took several decisions crippling Polish standing army to decrease the possibility of sedition and strived to get complete hold of some territory he could make his hereditary domain. He decided that the Livonia will be the best candidate, what drawn Poland into conflict with Sweden, also interested in that lands. Victory over Sweden could strengthen the position of August and could helped him to introduce absolutist monarchy in Poland. These goals were obviously conflicting with the pro-French and pro-liberal sympathies of Lubomirski (made great hetman of the Crown, or the chief commander of all Polish troops by August II who tried to get his support) and the king's defeat at Kliszów could be used as a proof that August II is not only a poor commander but also an inept king who has pulled the country into war he was unable to win. This political stance was a likely reason why Lubomirski decided to withdraw his troops from the battle paying only lip service to his orders and ultimately contributing to Swedish victory.

Lubomirski was not alone in his actions. Jan Sapieha, great hetman of the Lithuania (Lithuanian counterpart of Lubomirski) belonged to the powerful house of Sapieha that in late 17th century became a political power of its own, much to the chagrin of smaller noble houses in Lithuania who felt Sapiehas are abusing their power by consolidating key administrative and judicial offices in hands of a single family and using them to reinforce their hold over Lithuania. This caused the Lithuanian nobility to unite and defeat Sapieha's forces in what was essentially a local civil war in 1700. Fleeing from the country, Lithuanian hetman arrived at the court of Charles XII and asked for support, offering his service in defeating August II he blamed for allowing the civil war to happen.

So, one of the principal reasons for the defeat at Kliszów was that the commander of the Polish forces did what he could to undermine Saxon position in Poland by making the king look bad and weakening the Saxon military presence.