I like a lot that the Invictus Mod lets you play as Judea with a special storyline and adds other features to Judea like the Davidic and Zadokite Bloodlines. I am playing it on Easy since Judea is rated as Hard by the Mod.

I notice that when you start your playing, your ruler is Simon Zadokite b default, but the other famiilies vary, as do the High Priests. In real history however, it was a big deal to the Jews in that era that the dynasty of Zadok should also run the temple priesthood. The arrangement for the Zadokites or "Sons of Zadok" to run the Temple went back to David's time, and at the start of Antigonid Hellenic rule over Judea, the Zadokites were appointed both to run the Client State of Judea and to run the Temple priesthood. It was only about a century later that factional rivalry became strong enough that the Zadokites, particularly Onias' family, went into exile in Egypt, where they ran another Jewish temple at Leontopolis.

I picked a good wife with strong martial powers, and when I started a war with Nabatea, I clicked the option in the message to let her join my king in battle. But when actual fighting happened in a battle, her 8 point skill level didn't show up and my king with 4 skill points lost his battle to an enemy with 6 skill points.

Not very long after the game starts, Egypt will usually fight the Antingones successfully, and Egypt is much stronger than you, so it seems to be in your interest to fight on Egypt's side. So you can start the game by cutting your tribute from the Antigones, switching to Appease as your Diplomatic stance, and then improving relations with Egypt.

In the normal original game mode, Egypt still might not agree to an alliance with you because you are so much smaller- I have a red X on my option to ally with them when I start because it gives me -80 points on this request for being a much smaller rank than them (Egypt is big and I am small). So one option is to invade the Antigones when Egypt's war with them starts being effective. This worked for me when I played on Very Easy. Another method could be to get your rank higher after fighting small countries like Nabatea and then offer Egypt an alliance.

In the Invictus Mod however, your Mission Tree gives you a special option to join the Diadochi wars at the opening of your mission tree. I started my Invictus playthrough by conquering Nabatea (using my Levy + a 12 Martial Merc), but as I was doing so, Egypt successfully took over Antigones' lands surrounding my north side. It seems that you need to get a jump on the Diadochi Wars and be ready to fight Antigones as soon as Egypt starts sending in their armies. Otherwise, Egypt ends up with a huge chunk of Antigones' land with nothing left for you.

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I started the Judean Mission a second time, and began by attacking Nabatea. When I took Nabatea's capitol, Egypt began the Diadochi war, and when I took Nabatea's second fort and my war goal in Nabatea, Egypt already controlled the coast to the west of Judea, and sent soldiers north to Phoenicia. I made a peace deal with Nabatea that gave me Canaan and clientized the rest of Nabatea. Then I sent my forces north and took Syria for Egypt and occupied Gebal (a Phoenician city state under Egypt). At this point, I was surrounded by Ocean and by competing powers (the Seleucids) from advancing troops into Asia Minor against Antigones.

Does Egypt give you more land at the end of the Diadochi War if you capture more land for them as their ally?

My options for fighting alongside Egypt seem to be:
A. Conquer Nabatea and then join Egypt vs Syria in its Diadochi War, especially if Egypt doesn't give me much land at the end of the Diadochi war as a reward.
B. Conquer Nabatean Canaan and then clientize the rest of Nabatea, then march north to take Gebal and other Antigonid areas.
C. Start by declaring war on Antigones when the Ptolemies start fighting Syria well, so that I get all of Antigones' land that I occupy. Then when I have enough land, join Egypt's Diadochi War.

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Next, I tried option A above in order to see how much land Egypt would give me if I joined with them in the Diadochi War. I conquered Nabatea, and then joined Egypt's War. Egypt fought very well, taking the Levant from Antigones. Then on Feb. 1, 456 AUC, Egypt signed a peace deal with Antigones, ending the War even though Antigones still held on to territory. Egypt didn't give me any land as part of the deal. Then, I clicked the Mission button for "The Promised Land," whereby Egypt should give me all the land that they are occupying. But in fact, I didn't notice my borders changing at all after pressing the button.
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Next, I went with something like Option C - I used my War Council to get a Cassus Belli on Antigones (North Phoenicia) at the start of the game, then got an alliance offer from Egypt in the summer of 452 AUC, then I declared War on Antigones, choosing to invite Egypt into my War. This made me the "War Leader", meaning that I can assign my nation all territory captured during the war by my team, even though Egypt is stronger than me and Antigones, and will in effect win the war for me. Then I got a Mission Task Option to join the Diadochi Wars because Egypt and Antigones were now in combat.

Thus, this strategy seems to be the best option - using the War Council to get a Cassus Belli on Antigones (Fabricating a claim will take longer than it takes for the Diadochi Wars to start.) and improving Egypt's Relations in the Diplomacy menu, then getting a summer 452 Alliance offer from Egypt, then declaring war on Antigones, then choosing the Diadochi War Mission option.

In Invictus as Judea, you can ally with Egypt in the 2nd game year, invade Antigones independent of Egypt's Diadochi war, & get tons of land. If you conquer land as Judea w Egypt as your Ally in Invictus, Press the Diadochi War Task, make peace & press Promised Land, you lose land along the Judean coast.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2973004431

A small downside is that it's nice to start the game with a Cassus Belli on Nabatea from your War Council, so that you can expand your nation quickly and early. I am not a fan of "Fabricating a Claim" on Nabatea because I like to play with an ethical style instead of "Fabricating Claims".