“My centre is giving way, my right is in retreat; situation excellent. I shall attack.” General Foch, 8th September 1914 during the Battle of the Marne.

The end of the party conference season marks the end of the phoney war. On October 20th, the Comprehensive Spending Review will unveil the full horror of the cuts to come, sparking one of the most intense political battles Britain will have seen for decades.

On the surface, at least, the Coalition goes into battle stronger than many expected back in May. Relations between Lib Dem and Conservative ministers are said to be of the “we can finish each other’s jokes” category. In terms of policy, both Conservatives and Lib Dems continued to “bash the banks”, saying that it would be unacceptable for them to hand out high bonuses while not lending more to business (and while the rest of the country is feeling the pain of cuts). Fairness, responsibility, freedom, localism – these are the Coalition’s watchwords.

That said, differences continue to emerge on major issues – and those differences are not just Lib Dem vs Conservative, but Conservative vs Conservative and Lib Dem vs Lib Dem.  The immigration cap; student fees; welfare reform and support for families; the future of our nuclear deterrent: on all these issues, Conservatives and Lib Dems are creating a kaleidoscope of alliances to further (or block) changes in the face of other Ministers and MPs in their own parties.  If such alliances hold – for example, in calling for fundamental welfare reform – the Coalition will be, as David Cameron told his conference, “the radicals”. If not…

The challenge of resolving these differences is nothing compared with the political courage needed to see through the cuts. The furore over plans to cut child benefit is a taste of things to come. The surprising thing about the furore was not the policy itself: if the Coalition is to meet its fiscal targets while remaining true to its “fairness agenda”, those with the “broadest shoulders” will have to feel the pain too. The interesting thing was that, when under fire, the high command gave the impression of blinking, by suggesting that the change could be watered down – perhaps stung by accusations that they had misread who the “rich” are. When the whistle blows on October 20th and Ministers go over the top, their opponents will sniff out any such equivocation, and target it mercilessly. The Coalition needs to remember Foch’s words: attack is the best form of defence.

And those opponents will be lead by Ed Miliband. He knows full well that if Labour is to win back the 5 million voters it has lost since 1997, it has to appeal to what he calls “the mainstream majority” – to whom a left-leaning Labour Party in hoc to the trade unions is a distinctly dodgy proposition. Whether Miliband is able to appeal both to the “mainstream majority” and his trade union, “core” vote is one – perhaps the greatest – challenge he faces. Unlike Cameron and Blair, he has chosen not to take on “the core”, but is trying to play to both galleries. There are some “quick wins” he can pocket – policy “bones” which he can throw to both groups which will keep them happy and, ideally, will appeal to Lib Dem and Conservative floating voters. The obvious ones are being tough on banks and immigration, and standing up for the vulnerable in society.

Miliband’s choice of Shadow Cabinet will send the first signal of how he intends to grapple with this issue. Both the main contenders for Shadow Chancellor – Ed Balls and his wife, Yvette Cooper – believe the last Labour government’s deficit-reduction programme was too tough. Whether Miliband can create a credible critique of the Comprehensive Spending Review that appeals to the C2DEs – the group that deserted Labour in droves at the election – will decide his party’s success or failure.