Frederick V, Elector Palatine, has thrown in his lot with the Bohemian rebels to become the "Winter King,", but the Battle of White Mountain has seen the cause defeated in Bohemia, and the Protestant armies have been disbanded. Frederick's father-in-law, King James of England, has supported him, sending men and money. Now, in the autumn of 1621, the Elector's English army finds itself in the Palatine city of Frankenthal under the command of John Borres. With them are Protestant troops from Germany, as well as Walloon and Flemish soldiers.
A Catholic League army under Gonzalo de Cordoba has encircled Frankenthal - one of the most important cities in the Palatinate, along with Heidelberg and Mannheim - and prepares to besiege it. The English and their allies know that they can withstand the Imperialists for now, but they are also certain that their enemies will not stop trying. The city is too valuable, strategically situated on the Rhine as it is.
Below is a map of Frankenthal during the initial stage of the siege in 1621. The city lies directly to the west of the Rhine - across the river and little to the south is the fortress of Mannheim, another target of the Imperialists.
Frankenthal lies in a relatively flat plain, some distance from the river, so the besiegers can construct lines the entire way around the city, as we can see here. Approach from any direction is possible.
The campaign will be conducted using the Siege! application. Battles will be conducted using the While the Devil Rules tactical system, also from Application of Force. (We will include screen shots from the campaign app as appropriate - some do not depict the Thirty Years War, as the system cover sieges for the entirety of the Age of Vauban.)
The siege will be described as a series of events, including both tabletop actions and other types of background events of significance. The players are the leaders tasked with carrying out the orders of their superiors - they command in the field, but are responding to decisions made at a higher level (by the Emperor, the Elector, etc.). Thus, orders may come down to storm a breach, and the breach must be stormed, and so on. The Siege! application tracks the status of the two armies and the progress of the siege works, generates events, and indicates when a tabletop action must be fought, and what kind of scenario it will be. The GM designs the specific scenarios within guidelines provided by the app, according to the historical situation and the tabletop rules being used.
The Siege Begins: The attacker's army has invested Frankenthal, and the lines of circumvallation and contravallation around the city are in place. The siege has begun in earnest, and the bombardment of the place has started. Now, the approach trenches must be dug, so that the breaching batteries can do their work.

First Blow! The besieger's fire has struck a powder magazine, which has exploded and set some of the buildings in the city on fire. The besiegers cheer, while the garrison worries and takes stock of their remaining ammunition supplies.

Status: The attacker is confident of victory, but the defender's confidence is also high. There is currently no mining activity, nor any work on the approach trenches. The fortress walls remain undamaged.

Work on the Approach Trenches Proceeds: The attacker works on the approach trenches while his guns bombard the enemy fortress.

Status: The attacker is confident of victory, but the defender's confidence is also high. There is currently no mining activity, but the approach trenches are slowly making their way to the fortress walls from the west. The fortress walls remain undamaged, however.

Ordered to Storm a Demilune: Soldiers in one of the outworks have been causing casualties among the troops digging toward the city from the west, and Cordoba has decided to storm it. He assembles some of his Spanish veterans and other troops, and orders them to the assault.

The scenario can be found here.
The Catholic League assembles for the asault...
The English defenders are defiant!
The contest is furious!
The attack was a valiant one, with Cordoba's Spanish veterans and their German allies storming the outwork. The defenders responded blow-for-blow, and there was a massive struggle before the exhausted attackers were forced to withdraw.
The attacker's morale is depressed by their failed attempt and by the deaths of so many of their comrades, and the spirits of the defenders are raised in turn. Time passes, however, and the events begin to fade into the past...
Starvation! The defenders are running low on food...

Sickness! Worse yet, disease runs through the town...

State of Affairs: Despite defeating their besiegers, the lack of food and the outbreak of the fever are eating away at the defender's confidence. Outside the walls, the besieger is not so certain of victory, either. Both sides are still determined, however, so the siege continues.

By the Emperor's Command! Despite the initial repulse, word has come down that another attempt must be made. It is proving too difficult to drive the approach trenches toward the walls while the demilune remains to the defenders. This time, an even stronger force will be committed!

The scenario can be found here.