Yehoshaphat in Chronicles ii, teams up with Achav to fight. After, he is told off, saying one should not fight alongside the wicked or befriend them (19, 2). How can one fight in the Israeli army today? It seems like a DIRECT contradiction to this!

It seems like a strong question, but I'm sorry that you have a clear misunderstanding of the halachic status of the non-religious today. They are not at all wicked idolaters and murderers like Achav, who sinned more than any other king of Israel (M'lachim I, 16, 33), and is among the very few in all of Jewish history (!) who have no share in the world to come (Sanhedrin 10, 2). All halachic authorities today, from the Chazon Ish to Lubavitch and Rav Kook, all agree that we must relate with tolerance and love towards secular Jews as loving brothers, and not as evil people! Especially those who serve in the Israeli army, proving their mesirut nefesh, and dedication to Am Yisrael and Eretz Yisrael. If a Jew doesn't observe Shabbat, but does give charity, one must admire, respect and encourage that mitzva which he does. How much more so in reference to such a demanding and altruistic ideal of even being willing to give their lives Al kiddush Hashem. The halachic reasons and sources the poskim give are as follows, in a nutshell: 1. They did not receive religious education, so their status is like a baby who was kidnapped and raised by the gentiles, where he is "shogeg" and not to blame for his sins (Chazon Ish, Y.D 2, 28, based upon Rambam, hil. Shgagot 7, 2). 2. The Ramban relates to the collective sin of a generation, who mistakenly believes the Torah is "out-dated" for the "modern" world as "sh'gagat haEdah", another reason why they are not to blame for their sins (Ramban, Bamidbar 15, 22). 3. They are not at all like the murderer Achav, nor the hedonistic idolaters of the primitive world who had no ideology, and frequented the Avoda Zara temples for their physical pleasures of wine, meat, etc. Today's secular in Israel believe in humanism, Jewish nationalism, the Holy Hebrew Language, the Holy Land of Israel, the Holy Nation of Israel, and many truly religious ideals, even if they don't realize it (Rav Kook, Orot, p. 63). In addition, you are clearly not aware that 80% of Israelis ARE religious or traditional, and a far cry from the assimilated Jews which we know from America or the paganist murderers in Biblical times. Even secular soldiers clearly have much more mesirut nefesh for these ideals than the average Jew (only one who has served in the army can understand how difficult it really is). I personally heard from R. Shlomo Zalman Aurbach's driver, that R. ShZ often said that the holiest people in the world are the boys buried in the military cemetery on Mt. Herzl, and that's where he would go to daven by "Kivrei Tzadikim" (graves of the righteous, based on Bava Batra 10b). Apparently R. Shlomo Zalman Aurbach knows something that you need to learn on this topic, and I strongly suggest you do teshuva for mistakenly comparing these praise-worthy heroes, to be like Achav ymach Shmo (you obviously are also "shogeg" on this topic for you never learned it, but now you do know, and teshuva is for "shogeg", as well). 4. The Ba'al HaTania explains that the obligation of "V'Ahavta L'rei'acha" commands us to love each and every Jew, regardless of his actions, and how much more so if you have not even tried to patiently rebuke them (Tanya ch. 32)! 5. All Jews, even sinners, are considered the children of God which is an unconditional relationship- even if a child acts terribly. Accordingly, He loves us all, as we should as well, love our brothers (Kiddushin 36a, cited by Resp. Rashba 194). This clearly includes the obligation to save all Jews in the obligations of Milchemet Mitzva (= obligatory war of defense, Rambam hil. Milachim u'Milchamoteihem 5, 1), "not standing by your brother's blood" (Vayikra 19,16) and "saving from a rodef (pursuer, Rambam, Rotze'ach 1, 15), and how much more so, to save your fellow Jewish soldier who is trying to save you, as well. This is the most basic of common decency, that Torah observers should be the first ones to volunteer for the IDF, way before the non-religious. If you are really searching for an excuse to hate your fellow Jews today, you must journey to the Satmar Rov and his fellow extremists, who are clearly not accepted poskim by anyone except their immediate followers. All I can imagine is that perhaps someone is misinforming you, by trying to convince you not to live in Israel nor to serve in the IDF, by quoting such outdated and irrelevant excuses, as you have been citing. Chazal teach us that as opposed to Rav Yehuda, "living in the Land of Israel is equated with the rest of the mitzvot combined" (Sifre, Dvarim 12), and fighting for Israel even supersedes Shabbat! (Shulchan Aruch, Or.Ch. 330, 6) Apparently these questions preoccupy you greatly, and if you are really searching for the truth, as I wrote you previously, rather than continue to ask the same question in many different forms, I highly recommend for you to study the issue from the "roots", and systematically learn the sefer of one of the leading (formerly) anti-Zionist poskim, Rav Yissachar Teichtel HY"D, who was also greatly bothered by your question, regarding cooperating with our non-religious Zionists brothers. Only after the Nazi invasion, when he had to go into hiding, he had time and was forced to analyze the issue in depth, and wrote a 300 page book with thousands of sources and proofs: "Em HaBanim Smeicha" (also translated into English), changing his direction, and writing how the Talmudic and rabbinic sources actually obligate (!) to join with the secular Zionists to build the Holy Land. How much more so to protect Am Yisrael and Eretz Yisrael in today's milchemet mitzva [obligatory wars (Rambam hil. Milachim u'Milchamoteihem 5, 1)] against those who rise against us in our generation to obliterate us. These are very basic and central concepts in Jewish faith, which are clearly worth your while to clarify. All the best in your quest for truth! B'Ahavat Yisrael, Rav Ari Shvat