With the weather fast improving, US and British air attacks against the Republican Guard units south of Baghdad are moving into high gear.
Military sources also say that US marines have pushed northwards closer to the town of al-Kut on the Tigris river.
But the difficulties of fighting a multi-front war could well slow the pace of this military operation.
"The enemy we're fighting is different from the one we had war-gamed against," says Lieutenant General William Wallace, the senior US ground commander in Iraq.
Invading forces have not met the reception they were told to expect
His comments, made yesterday during a visit to the 101st Airborne Division, have reportedly caused some unease at the Pentagon, as they seem to illustrate that this campaign is not turning out quite as the US war planners expected.
Bad weather exacerbated the problems of long supply lines - a factor that could lead to a pause before the full-scale ground assault on the Republican Guard is launched.
But it is the level of opposition on the ground from irregular Iraqi units that is causing the greatest delay.
The Americans have had to battle to keep supply routes open.
The Euphrates valley is still far from secure and another thrust by the US Marine corps towards al-Kut on the Tigris river is facing similar resistance in towns like Qalat Sukkar.
Perceptions as to how this war would unfold seem to be very different in London and Washington.
There is a feeling here that the Pentagon's assessment of a rapid Iraqi collapse was based upon a poor understanding of the dynamics of Iraqi society.
As one senior British source put it, the United Kingdom's contribution was configured for medium-term success, although it could equally exploit a rapid Iraqi collapse.
That does not seem to be quite how the Pentagon saw it.
Weather and resistance are not the US planners' only problems.
The absence of a heavy US mechanised division moving southwards from the Turkish frontier means that it will be harder to pin down - or fix, as the military put it - the Republican Guard divisions protecting the northern approaches to the Iraqi capital.
Building up a force with any real combat power in the north is going to take time.
Many more US troops are on their way, but the first unit to arrive, the 4th Infantry Division, will not be ready for battle for some weeks yet.
Its troops are beginning to fly into Kuwait, but much of its heavy equipment is still at sea.
All the signs are that this war could be longer and harder than many people expected.