The direct military intervention that began in August 2016 is designed to block the continuous enclave of PKK-affiliated Syrian Kurds, and to clear the border areas of Islamic State (Daesh) militants. It also serves to establish a sanctuary for Turkey-backed Syrian Islamist rebels.
Turkey is keen on limiting the military intervention both temporally and territorially – if the Syrian government resolves to take a harsh stance against Kurdish autonomy in Rojava, Turkey is likely to make a de facto deal with the Syrian government.
If the Syrian government allows Kurdish autonomy within a federal state structure, Turkey will try to use both conservative Syrian Kurdish groups and proxy Islamist groups in order to destroy such an autonomous PKK-affiliated state structure next to its border.
Regarding Syria, Turkey is now returning to the long-held republican strategic culture that refrains from regime-change attempts in other countries.