Following Hamas' victory in PA Parliamentary elections
After having won the elections for the Legislative Council (Jan. 2006), Hamas found a growing interest in restraining its terror policy in light of several reasons:

• Political – Hamas' endeavor to first and foremost lay the foundations to its rule, including the establishment of a government in its leadership, as well as striving to influence all the Palestinian public. At the time Hamas had to consider other powerful factors, first of which are the PA and its security apparatuses.
• Military - the military wing promoted capacity buildup, in order to improve positions in the face of a future collision with Israel, and strived to secure its military superiority in the Gaza Strip versus the PA apparatuses.
  Furthermore, in several cases Hamas removed the curbs off its terror activity and executed attacks, namely the launchings of high trajectory rockets towards Israel. These attacks were always excused as retaliation against Lull "breaches" on the part of Israel and against loss of Palestinian lives.

In effect, these attacks emanated from inner-Palestinian considerations, mostly the shifting of political and public pressures off Hamas in Israel's direction. These are namely due to the following:

• The inner struggle between Hamas and Fatah in the Gaza strip, expressed in violent clashes between Fatah and its subordinate apparatuses and Hamas (since the end of May 2006 until May 2007).
• Inner pressures in Hamas and on the part of other terrorist entities not to halt "jihad" and armed struggle.
• Discontent among the Palestinian public regarding the social-economical and security situation, blaming Hamas for the death of Palestinian civilians.
• Hamas efforts to diminish unofficial understandings on which the "balance of deterrence" with Israel is based. Thus, as envisioned by Hamas, terror attacks serve the purpose of preserving the armed struggle while deterring Israel from retaliating.

Subsequently, Hamas policy lead to rounds of terrorist attacks throughout June 2006, Oct.-Nov. 2006 and May 2007, mainly manifested by:

• Extensive rocket launching – Hamas pushed towards a situation where Israel would pay the price for its thwarting activities against attacks originating in the Gaza Strip, and which Hamas perceived as violations of the cease-fire and the existing status quo.
• Stepping up attacks against Israel, namely on its borderline, by infiltrating through tunnels and placing explosive charges – a most prominent attack being the tunnel infiltration into Israel which enabled the kidnapping of Gilad Shalit into the Gaza Strip in June 2006.
• Intensive efforts to mount attacks in Israel through the Sinai (the U-Route). Throughout 2007 an average of three monthly attempts was noted. In January 2007 these efforts produced a suicide attack inside Israel (Eilat, causing 3 Israeli fatalities).      

Following the Gaza-Strip takeover
Having completed the seizing of control of the Gaza Strip (June 2007), Hamas attack policy included launching of mortar shells and executing attacks in the Gaza Strip surrounding area; yet, simultaneously refraining from launching rockets towards inner Israel.

Hamas assumed that Israel would avoid a harsh retaliation, despite the takeover of the Gaza Strip. Thus, Hamas tried to have the best of both worlds: to stabilize and sustain its rule in the Gaza Strip in order to allow its military strengthening without disturbance, meanwhile creating itself an image of a guardian of armed resistance and jihad against Israel.
This policy continued for seven months, during which rockets were launched towards Israel at a low key rate, mainly by other terrorist factions (dissidents), free of Hamas intervention or prevention, although Hamas itself undertook to refrain from it.

Since January till June 2008 Hamas initiated an escalation, and carried out three intensive rounds of rocket and mortar shell launchings towards Israel, aiming at redesigning the "retaliation equation" and make Israel pay a high price for each successful prevention.

At the time, a marked use of mortar-shells against Israel was noted, envisaged by Hamas as a tactical weapon of limited impact, exacerbating the shooting towards Israel, causing greater damage and casualties, yet, not crossing the barrier which would compel Israel to react forcefully.

However, 2008 saw a rise in high-scale attack-attempts, during which several mass murder attacks had been executed on border-crossings and on the Hoovers route. These were intended by Hamas (specifically the attack in the Kerem Shalom area on April 19, 2008) to promote a tie-break with Israel and force the lifting of the Gaza siege, at the face of the unsuccessful dialogue on the matter.

On the eve of Cast Lead – a deliberate escalation of Hamas terrorist activity
In the second half of 2008 the prevailing Lull (since June 19) saw a decrease in the scope of high trajectory shooting from the Gaza Strip towards Israel. With the end of the Lull in sight (Dec. 19), Hamas resolved not to prolong it in its present format but to try and achieve an "improved" Lull. This was mostly aimed at lifting the siege off the Gaza Strip and opening the border crossings with both Egypt (Rafah) and Israel, while not compromising the Lull's benefits, namely allowing Hamas to sustain its rule in Gaza. In order to achieve an "improved" Lull, Hamas promoted a controlled escalation, poising itself at a position of strength upon dissolving the present Lull.

Furthermore, ever since Nov. 2008 the Lull is slowly undermined. Following an Israeli assault thwarting a Hamas tunnel attack (during which six Hamas activists were killed and four IDF soldiers injured), Hamas retaliated in high trajectory shooting, and with the rise in the number of its casualties, intensified repercussion included shooting towards Ashkelon.

The situation deteriorated to a severe, unprecedented escalation of high trajectory shooting lead by Hamas. This eventually enhanced Israel's resolution to launch Cast Lead military operation in the end of Dec. 2008.

On a daily profile – throughout December 2008 there was a rise in the number of rocket and mortar shells launchings, specifically during the period between the end of the Lull and the beginning of Cast Lead, expressed in dozens of launchings compared to sporadic ones before.

On a monthly profile – throughout 2008 a significant extensive shooting is notable compared to the Lull's sporadic launches. Towards the end of the Lull and since November, there has been another increase in the number of launches. This data corroborates yet again the notion Hamas knowingly tried to cause an escalation, deliberately increasing the frequency of shooting: rockets – from about 150 in November to 440 in December; mortar shells – from about 95 to 300 in December.

Summary
The logic at the base of Hamas terrorist activity during this period and after Cast Lead, is characterized as follows:

1. Offensive capacity buildup – strengthening the military wing as an entity designated to fulfill Hamas' historic role as leader of an armed struggle against Israel from the Gaza Strip. This wing sustains high quantities and ever increasing arsenals of warfare means, namely high trajectory weapons, which Hamas intends to use against civilian and strategic targets in Israel, constantly extending the striking range.
2. Deffensive capacity buildup – Hamas constructed a defense layout and a buffer zone in the Gaza Strip, extensively booby-trapping territories and civilian houses, as well as a network of tunnels both on the edge of the urban zone and within densely populated areas. These enable to deter Israel from launching a ground assault against Hamas targets, and allow Hamas military wing to resist such assault by limiting IDF's maneuvering space and retaliation-capability, collecting a high Israeli death toll.
3. Hamas terrorist policy allows enough room between total refraining from attacks and controlled escalation – as a matter of routine, Hamas maintains a relative calm in the Gaza Strip while pursuing a gradual escalation, mainly through high trajectory shooting. These coincide with Hamas needs, being the stabilizing of its rule in the Gaza Strip, safeguarding Palestinian public support and mobilizing international public opinion to identify with Gaza inhabitants against Israeli actions (especially in the west). This policy diminishes Israel's legitimacy for retaliation and prevention.

As a consequence of the above, Israeli citizens and strategic assets became Hamas targets on the eve of Cast Lead in two ways:

1. The exacerbation of fire-power, number of rockets, range performance, guidance accuracy and warhead potency of high trajectory weapons – were all designed to increase the number of Israeli casualties and expand the territory under threat, including targets such as power stations, fuel storages, factories and hospitals.
2. Strengthening the military infrastructures within the Gaza Strip is destined to deter an Israeli incursion and restrict Israel's capability to foil attacks and strike terror infrastructures, rendering Hamas free to execute further high trajectory shooting towards Israeli civilian targets.

In the aftermath of Cast Lead, with diminishing political and military options in the Palestinian arena and against Israel (a stalemate in the reconciliation efforts, as well as deep controversies on substantial issues with the PA, inability to reach a Lull with Israel, a standstill in the economic plight) – resorting to military action remains a legitimate option for Hamas, subject to its discretion, a mechanism for breaking the ice and shifting attention from its own political incompetence towards Israel or the PA.