Let me know how this looks. It's pretty much what I had in mind after Palestine became independent, so all that's really changed is me describing what would have happened in the years for the timeskip. I think it also makes much more sense than my last summary.
Levantine History
Following the break away of Armenia, upper Syria immediately followed suit, starting it's own rebellion against the Ottoman Empire, while also effectively cutting off it's land access to Palestine, Jordan, Egypt and Libya. In an act of resentment, the Ottomans formed troops of able-bodied men from these four territories in order to combat the Syrians, while also basically sending them to their deaths, in order to wipe out anyone who could possibly send further territories into separate rebellions.
One of the soldiers of these units was a young Palestinian named Jellal, who, after losing his eye to a Syrian rebel, was discharged. However, before leaving for home, he overheard a conversation between two Turkish officers, explaining the purpose of the "Southern Brigades."
Immediately, he met up with a friend he had made while enlisted, and explained the situation to him. As word spread, many soldiers began to go missing, having run to Palestine to join the new rebel faction Jelal had started. Beginning by diverting supplies heading for Egypt, eventually a full-on confrontation began in Jerusalem, and the rebels were driven South to Beersheba, where they took over an Ottoman Military Base. From here they would operate until the Ottomans fell.
A month after taking Beersheba, the Palestinian rebels, along with their new friends who had rebelled and taken Jordan, worked together to secure Southern Palestine, and eventually began a march into SInai. Meanwhile, up North, the main force of the Palestinian rebels marched on Jerusalem, hoping to take their capital which would give them the supplies needed to end their war, and eventually focus fully on the occupation of Egypt. In order to fool the Ottomans, they sent a small group of mainly artillery as a diversion to the West of Jerusalem, while the main force snuck around the East. However, a "spy" had run to the Ottomans and told them of the Palestinian plan, hoping for a pardon when the rebellion was ended. Instead, he was executed, and the Ottoman army set up an ambush.
Just as they thought they were going to win, the rebel army was attacked from the North, East and South all at once. Spread out and disorganized, as well as outgunned against the Ottoman tanks, the rebels were driven to a corner, with most of their people wiped out. Just when things seemed their darkest, and when all hope had seemed lost, the Ethiopian army stormed in, taking out the Ottoman regiments and saving the PLA. After the city was taken, the surviving members of the PLA joined the Ethiopians until the Ottomans eventually collapsed, and ceded all rebels their territories.
With the Ottomans out of the way, most expected peace, but it was not going to happen. Tensions between Syria and Palestine rose, as both hoped to form a united Levant. However, exhausted from the rebellions, and low on resources, the conflict was a cold war more than anything. A few deaths along the border happened, but were generally rare.
Eventually, both sides realized that no progress was being made and agreed to sit down together and sort things out.
After months of shouting, talking and negotiating, it was decided that a union between the two states was optimal. The only issue that stuck was that of whether Jerusalem or Damascus would serve as the countries capital, which is still unresolved, thus the nation, in a sense, has two. Taking on the name of the Levantine Confederation, it now stands as a union of states in the Eastern Mediterranean, with close ties to Ethiopia thanks to their help in the Palestinian Liberation Campaign, with Jelal himself having even gone with the group of Palestinians that followed Ras Hassan back.