Yea, they may not be trained like our troops are, but they receive all they need from Iran and the supply depots that were raided following the fall of Saddam, high explosives.
You can stop a bullet, but not even a tank can stop a few thousand pounds of TNT equivalent explosion going off under it. They may have found the most effective weapons of the 20th century, home made at that. Its concerning.
There is no single "they" and part of the reason americans in particular are so confused and frustrated is that there is ZERO clarity in our leadership when they speak about what is actually fuckin happening there.
Our own President talks as if "they" are the same as al qaeda, to this day.
There are a range of sunni groups, baathist sub-groups, shiite groups and then ultra-islamacist foreign groups. And the kurds aint even rolled up their sleaves yet.
In simplistic terms, i see it this way (im sure in practice, the dozens of different groups may overlap at times):
1. Baathist & Fedayeen, pro-saddam and ex-regime folks with nothing to lose. These are the best trained fuckers as a category, many coming out of the Iraqi military elite and having real commanders with access to proper arms.
2. Shiite militias. They taste power. They want power. Shiites are the majority of the people and were repressed under Saddam. They are persian in heritage and angry. Al-Mahd and Sadr are the most dangerous. They are very territorial.
3. Sunni militias. They may or may not be tied with baathists, but they generally are more arab-leaning and scared of Shiite power. They refuse to back down to what they see as Shiite abuses. They are the minority and arent about to "let things slide" so when somebody gets attacked, they get even.
4. Al qaeda & foreign jihadists. These people flooded into iraq after we invaded, to cause trouble and to play heroes. They do a lot of nasty attacks and have successfully stirred up animosities between shiite and sunnies.
We fucked up by allowing #1 and #4 to emerge as they did. We needed to integrate more of the Baathists into the new government and society, instead of treating them all as criminals. We disbanded the entire Iraqi military and then pretended it was smart to start a new one from scratch without reaching out to some of the previous military leaders. We scared all these people and their families, making them outcasts and criminals even if they hated Saddam just as much as others did. Stupid. Backs to the walls, it just fed the flames and radicalized the forces. Only NOW are we seriously reaching out to Baathists. We're talking doctors, lawyers, educators and bureacrats who may have worked in Saddam's regime and have priviledges by birth/tribe but who may have fully welcomed change.
We fucked up by allowing foreigners to flood into iraq.
It's mind-numbing that we didnt control the borders, control the ammo depots, etc. Nobdy in iraq trusts each other years later, so al qaeda types can blow up a mosque and just let the sunnis and shiites rip into each other while everybody blames the USA. It's sickening what we've ALLOWED here.