Enemy fighters stationed in territories along the route of a strategic air bombing act similarly to AA guns. It is not compulsory to use them in this way but it is a free choice of the defender. The fighters so used may hit incoming bombers with a "1" of a die roll. Every fighter used in this strategic defense cannot attack in the next turn but can defend as usual if attacked.

It is allowed to escort bombers during Strategic Bombing Raids (SBR): every fighter may shoot enemy fighters down for each "1" tossed. This is not a conventional combat but it's a typical sequence of the SBR.

AAguns don't hit fighters but only bombers as usual.

Here is a clarifying example (hopefully):

2 US BMB based in UK attack Germany's IC and are escorted by 2 FTRs. Germany has 3 FTRs and a AAgun in its territory. The defender declares a strategic fighter defense using them all. Of course, in the next German turn those FTRs cannot be used to attack. Here it goes:

Escort US FTRs roll "1" and "3" => 1 hit (A German FTR is hit) Defender FTRs roll "1" "6" "3" => 1 hit (US FTR shot down) AAgun rolls for the BMBs "5" "4" => miss (Flak had no luck) Surviving BMBs roll 2+6= 8 IPCs of damage All planes return to base. If on the route back there are other FTRs activated for the strategic defense, the US planes must have other rounds of strategic combat.

Single FTRs cannot be used for strategic combats, they must escort bombers. Defending FTRs on carriers may be activated for strategic combat if they are along the route of the enemy bombers. Jet fighters (JFTR) may hit at every roll of 1 or 2 both as escorters and as defenders. Heavy Bombers roll 1 die as escort fighters.

Fighter leaders (i.e. Galland) add 1 as a bonus on each die roll, 2 or less for FTR, 3 or less for JFTRs.

Bomber leaders (i.e. Eaker) add a bonus on IPCs damage (See AxisRevenge - Leaders).