The Nationalist army won't attack Madrid with enough force to capture it. Even with the rest of the country conquered the Republican army in Madrid will hold out for years, fully supplied.

As Germany I will send volunteers to press the attack on Madrid (once I surround it) but even with German help the Nationalists won't throw in enough units to attack it. They attack for a day, lose org and call it off. Some script is keeping the army from committing to a strong attack?