Laughing out loud here.
For those newer players not "in the know" or players who have not seriously considered a "better" use for their oodles of extra transport, consider this;
a. for non-transport halftracks, they are considered standard combat units. When folks speak of halftracks in this thread, they are typically referring to the armored, armed version **that also is a transport.** Just thought I'd get that out of the way first.
b. German, U.S., and British (armed and armored) halftracks have radios. There is no reason why they could not carry out spotting functions (look at the antenna on the german HT in pic 2!!). It's important to discuss this with your opponent beforehand though, just to be sure if it's ok with him.
c. Of course, no unarmed transports, HT or not, are allowed to (deliberately) spot. Unarmored but *armed* halftracks are considered standard combat units, and are free to sacrifice themselves behind enemy lines whenever they wish (think german AAA halftracks)
d. This one is just my opinion (and that of many others); halftracks can spot, but due to their light armor and dual function as transports, make poor recon vehicles. Best to use low-value infantry units to spot for best results. If you really need ht's to spot though, or simply wish to take the risk, be certain you shut off the halftrack op-fire completely, and put him in a hard-to-reach spot, like forest, preferably with an escape route and at considerable distance from the enemy, if possible.
e. If your opponent is surrounding you with halftracks, then rest easy. You have lots of victory points coming to you (by way of burning halftracks), and you have received visual confirmation your opponent is desperate. If you wish to pull this highly dubious "strategy" on your opponent, or feel it should be allowed, be sure to discuss it with your opponent beforehand.
f. A clarification to "d" above. I make a distinction between "spotting" functions, and "recon" functions. A spotter is a machine gunner on a distant hilltop calling in artillery and airstrikes on enemies he sees in the valley below. A recon unit is something that drives around *in* the valley, looking for enemy HQ's, loaded units, security holes in the enemy line, etc. I'm perfectly happy with ht's carrying out spotting functions, but recon....I guess it could be done, but I can't imagine a commander approving of it, and also, they ht's would have a short life expectancy indeed. On the other hand, if my opponent used ht's as recon, I would not complain. Would I use ht's like this? I have before, but it's rare. All too often, there's simply no serious need to.
g. As far as using ht's during attacks? Best way to lose the game. Unless spotting or transporting things, the best use for a HT is to keep him deep in the forest. Halftracks have thin armor and horrible attack factors. Seriously, keep them away from the fighting. The only purpose for the armor is to make them resistant to artillery. The purpose of the mounted machine gun is to make adjacent enemy infantry disrupt or retreat on the rare occations they ambush you.
h. Using transport ht's (M3's, Bren carriers, 251/1) to draw op-fire. I usually keep my op-fire turned off if I even *think* I may be in a situation where enemy action can cause my armor to "spin" around to where they can then be spot in the sides or rear by other enemy units. I have never been a fan of op-fire. So, when an enemy tries this with me, the result is usually...utter silence. i just don't like the thought of my armor becoming spotted during the enemy turn. This is another one you need to discuss with your opponent beforehand. Also, if you think burning ht's to draw op-fire is some kind of a strategy for winning, you need to rethink your strategy. (hint: it doesn't work) Put sturdy infantry units out there instead (keep them in good terrain), and it will pay off.
Hope this was, um, informative. ;)