The time needed by the British to organise the landings meant that Sanders, Colonel Hans Kannengiesser and other German officers, supported by Esat Pasha (III Corps) had more time to prepare their defences. Sanders later noted, "the British allowed us four good weeks of respite for all this work before their great disembarkation ... This respite just sufficed for the most indispensable measures to be taken." Roads were constructed, small boats built to carry troops and equipment across the Narrows, beaches were wired and improvised mines were constructed from torpedo warheads. Trenches and gun emplacements were dug along the beaches and troops went on route marches to avoid lethargy. Kemal, whose 19th Division was vital to the defensive scheme, observed the beaches and awaited signs of an invasion from his post at Boghali, near Maidos. The Ottomans created a small air force with German assistance and had four aircraft operating around Çanakkale in February, conducting reconnaissance and army co-operation sorties. From 11 April, an Ottoman aircraft made frequent flights over Mudros, keeping watch on the assembly of the British naval force and an airfield was established near Gallipoli.