I'm going to take the time to explain "depot spawning" in order to help you find out where you can find instant infantry action: From the main map:

You have to double-click on the map to zoom in. If the red dots don't give you a good indication of where the battles are, then start by zooming in around Belgium. If you see only German cities, then scroll left until you see Allied cities. If you see only Allied cities, then scroll right. On the map there are front-line cities. These are cities that have an adjacent enemy city.

Notice how the non-frontline cities are greyed out a little, compared to the frontline cities. Let's look at the French-controlled city of Bastogne vs the German-controlled city of Wiltz.

Notice the black/orange infantry and armor icons by this city. This is EWS (early warning system). It means that the enemy has both ground and armor units near this city.

Between these two opposing cities there is usually an FB (Forward Base). If the cities are very close together then there isn't an FB for either side. This FB is used to spawn units closer to the enemy city. Only 1 side can have the FB at any given time. You can tell which city has the FB by clicking on the front-line city and looking for an icon with crossed swords. Currently in our example, wiltz (German) has the FB to Bastogne (French).

This means that the Germans can spawn all types of ground units at that FB. The French can spawn in Bastogne. The French could blow up this FB by using their engineers (sappers). If they succeeded then Bastogne would have the FB to Wiltz. Notice in this example how Bastogne has an explosion icon. This means that the Germans currently have at least one captured flag in that city. Let's find out a little more by clicking on Bastogne, then zooming the map in (using the zoom button "3x" on the interface):

Here we can see the 1 Army Base of Bastogne (tank icon), and the 5 depots (truck icon). There is a depot for every city that is adjacent to Bastogne. Players can spawn infantry at these depots in their own town, unless the depot has been captured by the enemy. To spawn at a depot, double-click it. If there is a mission, you can spawn there. Notice that one of these depots in Bastogne is German. Moving the mouse over that depot, we see that it is the Bastogne-Wiltz depot.

Under certain situations, a depot in an enemy city can spawn infantry for the attackers. Here are the criteria:

1) You own the city associated with the depot. In our example, this is the Bastogne-Wiltz depot. The Germans must own Wiltz to meet this criteria. CHECK

2) There are no enemy FBs between the city you own and the depot which has been captured. In our example, there cannot be a French FB between Bastogne and Wiltz. Looking back at this image:

We see that Germany has the FB between Wiltz and Bastogne. There can be only 1 FB between cities. In our example, if it is German, then France does NOT have an FB between these cities. So for criteria #2...no enemy FBs between the city you own and the depot which you have captured. CHECK.

3) You own the associated depot in your own city. Since every city has a depot associated with it's adjacent city...we realize there is a depot in Wiltz associated with Bastogne.

In order to spawn at the Wiltz depot in Bastogne...the Germans must own the Bastogne depot in Wiltz. CHECK.

4) You have owned the depot in the enemy city for X seconds. Currently, I think this is set to 2 minutes. After the depot has been initially captured, you must wait 2 minutes before a mission can be created there. After the mision is created, people can spawn in. So, here we have a prime opportunity for instant action, no matter what side you are on. The Germans can spawn in Bastogne (at this captured depot, and the French can also spawn in Bastogne (at their AB or any of their currently owned depots). The Germans will be trying to 1) defend that depot so that they can keep spawning, and 2) Capture other flags (especially if they are potentially spawnable depots, as well). Since the depot can only spawn infantry, the Germans will do a lot better if they have spawned armor at their FB and have already driven to Bastogne. The French will be trying to recapture that depot. Usually retaking a spawnable depot means suppressing it. The easiest way to do this is surround the depot with tanks and kill anything that moves. The depot will now be considered "camped", and if you spawn into a camped depot, you may find it very hard to make it out alive. Smoke grenades come in handy if you want to make a run for it.