When the message went out at 9 A.M. on Monday that Defense Minister Ehud Barak was going to hold a press conference two hours later, the assumption was that he had already made a deal with Tzipi Livni to run on a joint ticket on January 22. At the very least, he would issue a call to the parties of the center-left to unite, offering them his services. A potential resignation would have one purpose and one purpose only: to get back into office as soon as possible. In the two hours before he took the podium, reports were already going around that he would vacate his office by the end of the day, having had an angry exchange with the prime minister.

None of the assembled press corps (Barak's office had summoned diplomatic, political and security correspondents) were expecting what came next: a complete withdrawal from politics as soon as the next government is formed and a new defense minister appointed. Their disbelief grew when he said that the time had come "to allow other people to come in." Many listeners remained skeptical, especially when Barak refused to unequivocally deny a possible return to the Defense Ministry, inviting them enigmatically to "talk after January 22."

The consensus in political, military and media circles has been for years that Barak has one objective only. He doesn't care very much who will be the next prime minister, since he knows full well that it will never be him again. He is fixated on the Defense Ministry, convinced that it is his destiny to lead it since no other politician or ex-general has his wealth of experience, acumen and awe-inspiring decision-making capabilities. As he sees it, it would be a national disaster if Israel, with the multiple regional threats it will be facing in the foreseeable future, was to be deprived his services at the helm of the security establishment. Nothing he said or in his manner until Monday morning had indicated otherwise and not a murmur appeared anywhere of his intention to resign. On the contrary, buses and buildings in Tel-Aviv are plastered with Atzmaut election banners featuring his face, urging voters to vote for his new centrist party with a manifesto that could be summarized in five words: Barak must remain defense minister. So what prompted this sudden about-face?

We could of course take him at his word when he says that at the age of 70 he "wants to study, read, live, have a good time." We could believe that at the age of 70, all he wants is to spend more time with his grandchildren, travel the world and play Chopin on his baby grand. But that flies in the face of everything he has said and done in 53 years of service, with only a brief pause as a private consultant that cashed up a few millions, that he can't allow himself to desert the struggle for Israel's existence.

It's not just the Atzmaut campaign that made the impression that he's trying to stay on, but also the fact that Barak has been in talks with Livni for weeks about a possible joint run. If he could have his way, he would be very content to continue serving under Benjamin Netanyahu. The two men know each other from their days together in the elite Sayeret Matkal commando unit in the late 1960s. Then, Barak was the senior. The two men have worked together in virtually complete harmony for the last four years. Barak was closer and more loyal to Bibi than any of his Likud ministers. A couple of months ago there was a very brief period of discord when it seemed that Barak was rethinking his hitherto rock-solid support for a strike on Iran without coordinating his statements with the prime minister. But they seem to have smoothed things over very quickly.

But in recent weeks, Barak has finally realized that his chances of remaining Netanyahu's defense minister are increasingly slim. Not because Bibi doesn't want him by his side; it's simply because the odds are against him.

Barak has long been a hate-figure for the right-wing element in the Likud who blame him for blocking construction in the settlements and occasionally dismantling outposts. For months, while rumors said that Netanyahu might award him a spot on the Likud list – the prime minister had voiced the possibility that as party leader he would be allowed to "parachute" his own candidates into the list, which widely assumed to be for Barak's benefit – he faced mounting pressure from his own party ranks against the motion. They didn't really care whether Barak would become a Likud member or not; they just didn't want to see him in the next cabinet altogether. One reason why former IDF Chief of Staff and Likud minister Moshe Ya'alon was expected to do well in the Likud primaries is that many members want to make it clear to Netanyahu that he is their candidate for defense minister.

Barak realized that even if Atzmaut would succeed in securing him a seat in the next Knesset, an outcome far from assured, Netanyahu would be unable to reappoint him to the only cabinet position he has any interest in. That was the moment he knew he had to resign and become master of his political fate. The short flirt with Livni may have been a last grasp at straws but he knew by then that he may as well leave the IDF headquarters in Tel Aviv, for the last time, with his head held high.

This doesn't mean we have seen the last of Ehud Barak in Israeli public life. For as long as he is healthy - and he is certainly a sprightly septuagenarian - he will remain lurking in the background and there will be periodical calls to bring him back, just like Moshe Dayan who was appointed defense minister in 1967 by a reluctant Levi Eshkol in the dark days of "the waiting period" on the eve of the Six Day War. And you can bet that when the opportunity arises, he will immediately report for duty.

Barak may be an old soldier but he has no intention of fading away.