my experience be careful anyway, but both works, do not forget Antibiotics , especially if someone pushes from below, sometimes pulling out the baby by feet first from the top helps but this might mean that you have to do a T incision in the uterus , so next delivery CS ....

It is best to avoid this situation, by carefully following the distracted labor process.

This is not an easy question, with a single correct answer as it depends on the situation very much.

Previous surgical history, BMI and gravidity of the mother, size of the baby, the duration of the impaction, the skill of the surgeon, the experience of the team all matters.

The time of the event is also important. Such cases tend to occur in very late at night or early in the morning where there is usually minimal help available.

You (and the baby and mother) would be very lucky if you have a "24 hour ready operation room" with good helping hands, doctors, assistants or midwives, around in a large hospital, with a transfusion center.

Sometimes a steady and gradual traction of the baby by the shoulders without squeezing the neck helps to slide and pull up the fetal head during cesarean. If you have an experienced helper with trained hands with good control and skills and reasonable movements, this person may help by simultaneously pushing the fetal head from below, while you do the controlled pulling from the above. However, uncontrolled power is not a real power, and can be dangerous. Sudden and jerky movements are very dangerous and not wanted. Pressing the anterior fontanel or depression fractures of the skull may occur with uncontrolled or untrained hands. These may cause injuries. Three or four fingers of the hand could be better to push the head by holding them in a triangular or quadrangular fashion, therefore the power of pushing could be distributed, rather than pushing from a single point.

Incision to the uterus must be very careful also because the lower segment would probably be extremely thinned. Uncontrolled extension of the incision to lateral or cutting the infant could be possible. Classical uterine incision may be an option in selected cases, however, there is a serious chance of atony after such a vigorous labor. The incision may still extend downwards. This is also hard to repair and still bleeds a lot even if there is no atony.

Neonatologist or a pediatrician is a wonderful help and should be available if possible. These babies may require active resuscitation.

Again:

It is best to avoid the situation with good labor management.

Thanks @ kasim. This type of scenario is a very common presentation in developing countries where access to health care is low. Patients prefer to labour and deliver at hope and often present to you with obstructed labour. Definitely patient that have skilled birth attendant at delivery.